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27 Aug
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MJO and Teleconnections 27 Aug, 03:00
19 Aug
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Dear Colleagues,
Please join us for the August webinar hosted by the WWRP/WCRP/S2S/MJO and Teleconnections sub-project.
Title: Predictability of Sahelian heatwaves and importance of tropical modes of variability
Speaker: Guigma Kiswendsida, Red Cross Red Crescent Climate CenterDate: Thursday, August 26, 2021
Time: 1:00pm EDT | 5:00pm UTCAbstract
Heatwaves are a growing threat to human health worldwide, but remain poorly documented over Africa. This study addresses the predictability of Sahelian heatwaves during the February-March and April to June seasons as well as their large-scale drivers, with a focus on the role of the Madden-Julian Oscillation (MJO), the equatorial Rossby (ER) and Kelvin (EK) waves. The ECMWF ENS extendedrange forecasting system (ENS-ext), with a forecast horizon of 46 days, is used for the prediction skill assessment, the ERA5 reanalysis being the main reference dataset. Heatwaves are defined as spells of three or more consecutive days, where a given thermal index exceeds both the 75th percentile of its total distribution and the 90th percentile of its calendar day distribution. Tropical modes are obtained through a wavenumber-frequency decomposition of OLR anomalies.The results show that ENS-ext is able to predict heatwaves with relatively good skill out to two to three weeks ahead. The highest forecast scores are obtained for daytime heatwaves and for the shortest leadtimes. With increasing lead-times, heatwaves become more predictable at nighttime than at daytime. Likewise, the prediction skill is initially higher during the February-March season for the shortest leadtimes, whereas for week 2 of the forecast and beyond, the April to June season heatwaves have a better predictability.
Tropical modes significantly affect the occurrence of heatwaves in the Sahel. Depending on their convective phase, they can either increase or decrease their probability. The MJO has the greatest effect, closely followed by the ER wave whereas the EK wave is less important to heatwave occurrence.
The observed relationship between heatwave occurrence and tropical mode activity is relatively well simulated by ENS-ext. The heatwave prediction skill is also found to be higher when the MJO and the ER wave are predicted to be active than when they are predicted to be inactive. Whilst this gain in prediction skill is limited to the first week of forecast for the ER wave, it extends out to the third week for the MJO.
Therefore, improving the representation of tropical modes in models will positively impact heatwave prediction at the subseasonal scale in the Sahel, and gain more time and precision for anticipatory actions.
If you would like to attend the webinar, please email to cstan AT gmu DOT edu
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Dear Colleagues,
Please join us for the August webinar hosted by the WWRP/WCRP/S2S/MJO and Teleconnections sub-project.
Title: Predictability of Sahelian heatwaves and importance of tropical modes of variability
Speaker: Guigma Kiswendsida, Red Cross Red Crescent Climate CenterDate: Thursday, August 29, 2021
Time: 1:00pm EDT | 5:00pm UTCAbstract
Heatwaves are a growing threat to human health worldwide, but remain poorly documented over Africa. This study addresses the predictability of Sahelian heatwaves during the February-March and April to June seasons as well as their large-scale drivers, with a focus on the role of the Madden-Julian Oscillation (MJO), the equatorial Rossby (ER) and Kelvin (EK) waves. The ECMWF ENS extendedrange forecasting system (ENS-ext), with a forecast horizon of 46 days, is used for the prediction skill assessment, the ERA5 reanalysis being the main reference dataset. Heatwaves are defined as spells of three or more consecutive days, where a given thermal index exceeds both the 75th percentile of its total distribution and the 90th percentile of its calendar day distribution. Tropical modes are obtained through a wavenumber-frequency decomposition of OLR anomalies.The results show that ENS-ext is able to predict heatwaves with relatively good skill out to two to three weeks ahead. The highest forecast scores are obtained for daytime heatwaves and for the shortest leadtimes. With increasing lead-times, heatwaves become more predictable at nighttime than at daytime. Likewise, the prediction skill is initially higher during the February-March season for the shortest leadtimes, whereas for week 2 of the forecast and beyond, the April to June season heatwaves have a better predictability.
Tropical modes significantly affect the occurrence of heatwaves in the Sahel. Depending on their convective phase, they can either increase or decrease their probability. The MJO has the greatest effect, closely followed by the ER wave whereas the EK wave is less important to heatwave occurrence.
The observed relationship between heatwave occurrence and tropical mode activity is relatively well simulated by ENS-ext. The heatwave prediction skill is also found to be higher when the MJO and the ER wave are predicted to be active than when they are predicted to be inactive. Whilst this gain in prediction skill is limited to the first week of forecast for the ER wave, it extends out to the third week for the MJO.
Therefore, improving the representation of tropical modes in models will positively impact heatwave prediction at the subseasonal scale in the Sahel, and gain more time and precision for anticipatory actions.
If you would like to attend the webinar, please email to cstan AT gmu DOT edu
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30 Jul
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Dear Colleagues,
Please join us for the July webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: Linear inverse modeling: A framework for subseasonal forecasting and the diagnosis of physical sources of forecast skill
Speaker: John Albers, NOAA PSL/CIRES/University of Colorado BoulderDate: Thursday, July 29, 2021
Time: 10:30am EST | 2:30pm UTCAbstract
We introduce the linear inverse model (LIM) framework and discuss its application as a subseasonal forecast model, a free-running climate model, and as a tool to isolate physical sources of subseasonal forecast skill. A LIM is an observationally based, statistical-dynamical model that approximates the chaotic evolution of a ‘coarse-grained’ climate anomaly as the sum of slowly evolving, predictable linear dynamics and rapidly evolving, unpredictable white noise. Here we construct a LIM that models the coupled dynamics of tropical heating, tropical sea-surface temperatures, extratropical tropospheric and stratospheric dynamical variability, and 2m temperature. Using this LIM, we examine the predictability and sources of forecast skill of the North Atlantic Oscillation (NAO) and the record breaking February 2021 North American cold air outbreak (CAO). First, we demonstrate that the LIM can be used to decompose the dynamics that drive NAO variability and predictability. A LIM-based dynamical (‘nonnormal’) filter identifies those dynamical modes that, despite capturing only a fraction of overall NAO variability, are largely responsible for extended-range NAO skill. Predictable NAO events stem from the linear superposition of these modes, which represent joint tropical sea-surface temperature-lower stratosphere variability plus a single mode capturing downward propagation from the upper stratosphere. The joint tropical-stratosphere modes are associated with non-canonical ENSO teleconnections that extend upwards into the lower stratosphere, while the downward propagating mode captures stratospheric NAM anomalies that are commonly associated with sudden stratospheric warmings. The predictable LIM subspace identifies high skill NAO forecasts, both for the LIM and for the state-of-the-art European Centre for Medium-Range Weather Forecasts Integrated Forecast System (IFS), for the 1997-2016 period. For the 2021 CAO, the LIM had high confidence in a cold surge at least 4 weeks in advance of the event onset, which was contrary to the dynamical forecast model guidance. When the LIM’s nonnormal filter is applied to the CAO, it is shown that the cold surge was due primarily to (predictable) SST-stratosphere based teleconnections and (unpredictable) internal variability, with small cold anomaly contributions from the MJO and the early January sudden stratospheric warming.If you would like to attend the webinar, please email to cstan AT gmu DOT edu
Meeting Recording:
https://gmu.zoom.us/rec/share/MSf8LdLWs0wyFsVMUaB3G5dDwSPXazmho2BUNWDyT71N9o789eV1fY3R3CWsE1sh.S0G8eS1PlxxRFFRT -
Dear Colleagues,
Please join us for the July webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: Linear inverse modeling: A framework for subseasonal forecasting and the diagnosis of physical sources of forecast skill
Speaker: John Albers, NOAA PSL/CIRES/University of Colorado BoulderDate: Thursday, July 29, 2021
Time: 10:30am EST | 2:30pm UTCAbstract
We introduce the linear inverse model (LIM) framework and discuss its application as a subseasonal forecast model, a free-running climate model, and as a tool to isolate physical sources of subseasonal forecast skill. A LIM is an observationally based, statistical-dynamical model that approximates the chaotic evolution of a ‘coarse-grained’ climate anomaly as the sum of slowly evolving, predictable linear dynamics and rapidly evolving, unpredictable white noise. Here we construct a LIM that models the coupled dynamics of tropical heating, tropical sea-surface temperatures, extratropical tropospheric and stratospheric dynamical variability, and 2m temperature. Using this LIM, we examine the predictability and sources of forecast skill of the North Atlantic Oscillation (NAO) and the record breaking February 2021 North American cold air outbreak (CAO). First, we demonstrate that the LIM can be used to decompose the dynamics that drive NAO variability and predictability. A LIM-based dynamical (‘nonnormal’) filter identifies those dynamical modes that, despite capturing only a fraction of overall NAO variability, are largely responsible for extended-range NAO skill. Predictable NAO events stem from the linear superposition of these modes, which represent joint tropical sea-surface temperature-lower stratosphere variability plus a single mode capturing downward propagation from the upper stratosphere. The joint tropical-stratosphere modes are associated with non-canonical ENSO teleconnections that extend upwards into the lower stratosphere, while the downward propagating mode captures stratospheric NAM anomalies that are commonly associated with sudden stratospheric warmings. The predictable LIM subspace identifies high skill NAO forecasts, both for the LIM and for the state-of-the-art European Centre for Medium-Range Weather Forecasts Integrated Forecast System (IFS), for the 1997-2016 period. For the 2021 CAO, the LIM had high confidence in a cold surge at least 4 weeks in advance of the event onset, which was contrary to the dynamical forecast model guidance. When the LIM’s nonnormal filter is applied to the CAO, it is shown that the cold surge was due primarily to (predictable) SST-stratosphere based teleconnections and (unpredictable) internal variability, with small cold anomaly contributions from the MJO and the early January sudden stratospheric warming.If you would like to attend the webinar, please email to cstan AT gmu DOT edu
Meting Recording:
Topic: S2S/MJO-Teleconnections Monthly Webinar
Date: Jul 29, 2021 09:53 AM Eastern Time (US and Canada)Meeting Recording:
https://gmu.zoom.us/rec/share/MSf8LdLWs0wyFsVMUaB3G5dDwSPXazmho2BUNWDyT71N9o789eV1fY3R3CWsE1sh.S0G8eS1PlxxRFFRT -
Dear Colleagues,
Please join us for the June webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: On the relationship between intraseasonal and interannual teleconnections from Indo-Pacific heating
Speaker: Franco Molteni, ECMWFDate: Thursday, June 24, 2021
Time: 10:30am EST | 2:30pm UTCAbstract
Many studies on the extratropical teleconnections of the Madden-Julian Oscillation (MJO) in boreal-winter have associated an increased frequency of positive North Atlantic Oscillation (NAO) anomalies with the occurrence of MJO phase-3 10 to 15 days earlier, when increased convection is located in the eastern Indian Ocean. Connections between the NAO and the MJO phase-2 (when increased convection is located further west) appear to be weaker in intra-seasonal diagnostics.
On the other hand, on the interannual time scale, teleconnections computed from 2-month or 3-month means indicate a stronger connection of positive NAO with convection in the western-to-central part of the tropical Indian Ocean.This discrepancy between results on the two time-scales are due, to a large extent, to the impact of ENSO on the inter-annual component of Indian Ocean circulation and heating anomalies. This implies that the way in which the seasonal-to-interannual signal is (or is not) filtered out may significantly affect the estimation of intra-seasonal teleconnections. Since the impact of ENSO on both Indian Ocean convection and the NAO varies between early and late winter, results are also dependent on the specific period of the year considered.
In this talk, diabatic heating computed from ERA-5 data (specifically, as a residual between total and adiabatic temperature tendencies) in a 36-year period, and 200-hPa geopotential height from the same re-analysis, are used to investigate the relationship between inter-annual and intra-seasonal teleconnections of MJO-like heating anomalies over the Indian Ocean and the Maritime Continents. Results show that the interannual signal dominates the NAO teleconnection from the Indian Ocean in early winter (Nov.-Dec.); in this period the interannual teleconnections from the western and eastern part of the ocean are anti-correlated over the North Atlantic, and differ significantly from the intra-seasonal signals. Later in the winter (Jan.-Feb.), intraseasonal variability explains a larger fraction of the large-scale diabatic heating variance, and intra-seasonal teleconnections are more similar to those computed without any scale separation.
Finally, results from a set of sub-seasonal ensembles run with the ECMWF coupled model, and initialized on 1 Nov. 1981 to 2016, will be compared with ERA-5 results for the Nov.-Dec. period. Confirming earlier findings on ECMWF sub-seasonal forecasts, a good agreement is found on the patterns of tropical heating variability, but the amplitude of their extratropical teleconnections is significantly under-estimated.
If you would like to attend the webinar, please email to cstan AT gmu DOT edu
Meeting Recording:
https://gmu.zoom.us/rec/share/FGzhe-QBQDfHQcR_PRABSEPpLY8kiDSqk7ANn7Kfh7Rs3Y6aliLkYVcQqEuPrCaD.4zpTyrTkNIQqOM10 -
Dear Colleagues,
Please join us for the July webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: Linear inverse modeling: A framework for subseasonal forecasting and the diagnosis of physical sources of forecast skill
Speaker: John Albers, NOAA PSL/CIRES/University of Colorado BoulderDate: Thursday, July 29, 2021
Time: 10:30am EST | 2:30pm UTCAbstract
We introduce the linear inverse model (LIM) framework and discuss its application as a subseasonal forecast model, a free-running climate model, and as a tool to isolate physical sources of subseasonal forecast skill. A LIM is an observationally based, statistical-dynamical model that approximates the chaotic evolution of a ‘coarse-grained’ climate anomaly as the sum of slowly evolving, predictable linear dynamics and rapidly evolving, unpredictable white noise. Here we construct a LIM that models the coupled dynamics of tropical heating, tropical sea-surface temperatures, extratropical tropospheric and stratospheric dynamical variability, and 2m temperature. Using this LIM, we examine the predictability and sources of forecast skill of the North Atlantic Oscillation (NAO) and the record breaking February 2021 North American cold air outbreak (CAO). First, we demonstrate that the LIM can be used to decompose the dynamics that drive NAO variability and predictability. A LIM-based dynamical (‘nonnormal’) filter identifies those dynamical modes that, despite capturing only a fraction of overall NAO variability, are largely responsible for extended-range NAO skill. Predictable NAO events stem from the linear superposition of these modes, which represent joint tropical sea-surface temperature-lower stratosphere variability plus a single mode capturing downward propagation from the upper stratosphere. The joint tropical-stratosphere modes are associated with non-canonical ENSO teleconnections that extend upwards into the lower stratosphere, while the downward propagating mode captures stratospheric NAM anomalies that are commonly associated with sudden stratospheric warmings. The predictable LIM subspace identifies high skill NAO forecasts, both for the LIM and for the state-of-the-art European Centre for Medium-Range Weather Forecasts Integrated Forecast System (IFS), for the 1997-2016 period. For the 2021 CAO, the LIM had high confidence in a cold surge at least 4 weeks in advance of the event onset, which was contrary to the dynamical forecast model guidance. When the LIM’s nonnormal filter is applied to the CAO, it is shown that the cold surge was due primarily to (predictable) SST-stratosphere based teleconnections and (unpredictable) internal variability, with small cold anomaly contributions from the MJO and the early January sudden stratospheric warming.If you would like to attend the webinar, please email to cstan AT gmu DOT edu
Meting Recording:
https://gmu.zoom.us/rec/share/1tYHPeJKbLGlasTJJlZ1uY5Y2lt_S_383WVnQTBAGj88QA1oNI6RTKYwVu5HLkB-.slwpmxZllNxDwOfS Passcode: 0c6%b#5?
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28 Jun
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MJO and Teleconnections 28 Jun, 21:25
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Dear Colleagues,
Please join us for the June webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: On the relationship between intraseasonal and interannual teleconnections from Indo-Pacific heating
Speaker: Franco Molteni, ECMWFDate: Thursday, June 24, 2021
Time: 10:30am EST | 2:30pm UTCAbstract
Many studies on the extratropical teleconnections of the Madden-Julian Oscillation (MJO) in boreal-winter have associated an increased frequency of positive North Atlantic Oscillation (NAO) anomalies with the occurrence of MJO phase-3 10 to 15 days earlier, when increased convection is located in the eastern Indian Ocean. Connections between the NAO and the MJO phase-2 (when increased convection is located further west) appear to be weaker in intra-seasonal diagnostics.
On the other hand, on the interannual time scale, teleconnections computed from 2-month or 3-month means indicate a stronger connection of positive NAO with convection in the western-to-central part of the tropical Indian Ocean.This discrepancy between results on the two time-scales are due, to a large extent, to the impact of ENSO on the inter-annual component of Indian Ocean circulation and heating anomalies. This implies that the way in which the seasonal-to-interannual signal is (or is not) filtered out may significantly affect the estimation of intra-seasonal teleconnections. Since the impact of ENSO on both Indian Ocean convection and the NAO varies between early and late winter, results are also dependent on the specific period of the year considered.
In this talk, diabatic heating computed from ERA-5 data (specifically, as a residual between total and adiabatic temperature tendencies) in a 36-year period, and 200-hPa geopotential height from the same re-analysis, are used to investigate the relationship between inter-annual and intra-seasonal teleconnections of MJO-like heating anomalies over the Indian Ocean and the Maritime Continents. Results show that the interannual signal dominates the NAO teleconnection from the Indian Ocean in early winter (Nov.-Dec.); in this period the interannual teleconnections from the western and eastern part of the ocean are anti-correlated over the North Atlantic, and differ significantly from the intra-seasonal signals. Later in the winter (Jan.-Feb.), intraseasonal variability explains a larger fraction of the large-scale diabatic heating variance, and intra-seasonal teleconnections are more similar to those computed without any scale separation.
Finally, results from a set of sub-seasonal ensembles run with the ECMWF coupled model, and initialized on 1 Nov. 1981 to 2016, will be compared with ERA-5 results for the Nov.-Dec. period. Confirming earlier findings on ECMWF sub-seasonal forecasts, a good agreement is found on the patterns of tropical heating variability, but the amplitude of their extratropical teleconnections is significantly under-estimated.
If you would like to attend the webinar, please email to cstan AT gmu DOT edu
Meeting Recording:
Topic: S2S/MJO-teleconnections Monthly Webinar
Start Time : Jun 24, 2021 09:52 AMMeeting Recording:
https://gmu.zoom.us/rec/share/FGzhe-QBQDfHQcR_PRABSEPpLY8kiDSqk7ANn7Kfh7Rs3Y6aliLkYVcQqEuPrCaD.4zpTyrTkNIQqOM10
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17 Jun
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MJO and Teleconnections 17 Jun, 23:17
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Dear Colleagues,
Please join us for the June webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: On the relationship between intraseasonal and interannual teleconnections from Indo-Pacific heating
Speaker: Franco Molteni, ECMWFDate: Thursday, June 24, 2021
Time: 10:30am EST | 2:30pm UTCAbstract
Many studies on the extratropical teleconnections of the Madden-Julian Oscillation (MJO) in boreal-winter have associated an increased frequency of positive North Atlantic Oscillation (NAO) anomalies with the occurrence of MJO phase-3 10 to 15 days earlier, when increased convection is located in the eastern Indian Ocean. Connections between the NAO and the MJO phase-2 (when increased convection is located further west) appear to be weaker in intra-seasonal diagnostics.
On the other hand, on the interannual time scale, teleconnections computed from 2-month or 3-month means indicate a stronger connection of positive NAO with convection in the western-to-central part of the tropical Indian Ocean.This discrepancy between results on the two time-scales are due, to a large extent, to the impact of ENSO on the inter-annual component of Indian Ocean circulation and heating anomalies. This implies that the way in which the seasonal-to-interannual signal is (or is not) filtered out may significantly affect the estimation of intra-seasonal teleconnections. Since the impact of ENSO on both Indian Ocean convection and the NAO varies between early and late winter, results are also dependent on the specific period of the year considered.
In this talk, diabatic heating computed from ERA-5 data (specifically, as a residual between total and adiabatic temperature tendencies) in a 36-year period, and 200-hPa geopotential height from the same re-analysis, are used to investigate the relationship between inter-annual and intra-seasonal teleconnections of MJO-like heating anomalies over the Indian Ocean and the Maritime Continents. Results show that the interannual signal dominates the NAO teleconnection from the Indian Ocean in early winter (Nov.-Dec.); in this period the interannual teleconnections from the western and eastern part of the ocean are anti-correlated over the North Atlantic, and differ significantly from the intra-seasonal signals. Later in the winter (Jan.-Feb.), intraseasonal variability explains a larger fraction of the large-scale diabatic heating variance, and intra-seasonal teleconnections are more similar to those computed without any scale separation.
Finally, results from a set of sub-seasonal ensembles run with the ECMWF coupled model, and initialized on 1 Nov. 1981 to 2016, will be compared with ERA-5 results for the Nov.-Dec. period. Confirming earlier findings on ECMWF sub-seasonal forecasts, a good agreement is found on the patterns of tropical heating variability, but the amplitude of their extratropical teleconnections is significantly under-estimated.
If you would like to attend the webinar, please email to cstan AT gmu DOT edu
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21 May
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MJO and Teleconnections 21 May, 03:56
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Dear Colleagues,
Please join us for the May webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: The importance of a stratospheric route for MJO teleconnections to the Euro-Atlantic sector
Speaker: Chaim Garfinkel, Hebrew UniversityDate: Thursday, May 27, 2021
Time: 1:30pm EST | 5:30pm UTCAbstract
The effect of the Madden‐Julian Oscillation (MJO) on the Northern Hemisphere wintertime stratospheric polar vortex and major, mid‐winter stratospheric sudden warmings (SSWs) is evaluated using a meteorological reanalysis dataset. The MJO influences the region in the tropospheric North Pacific sector that is most strongly associated with a SSW. Consistent with this, SSWs in the reanalysis record have tended to follow certain MJO phases. SSW events are more predictable if they are preceded by an MJO event. The magnitude of the influence of the MJO on the vortex is comparable to that associated with the Quasi‐Biennial Oscillation and El Niño. The MJO could be used to improve intra‐seasonal projections of the Northern Hemisphere high latitude circulation, and in particular of the tropospheric Northern Annular Mode and North Atlantic Oscillation, at lags exceeding one month. The ability of operational subseasonal forecasting models archiving their data as part of the S2S project to capture this is assessed, and most models are found to underestimate the magnitude of the observed effect.If you would like to attend the webinar, please email to cstan AT gmu DOT edu
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14 May
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MJO and Teleconnections 14 May, 10:01
12 May
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Applications 12 May, 16:39
30 Apr
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MJO and Teleconnections 30 Apr, 02:55
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Dear Colleagues,
Please join us for the April webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: Tropical origins of Weeks 2-4 forecasts errors during Northern Hemisphere cool season
Speaker: Juliana Dias, NOAA, Physical Sciences LaboratoryDate: Thursday, April 29, 2021
Time: 10:30am EST | 2:30pm UTCAbstract
A set of 30-day reforecast experiments is used to quantify the remote impacts of tropical forecast errors on the National Centers for Environmental Prediction (NCEP) global forecast system (GFS). The approach is to nudge the model towards reanalyses in the tropics and then measure the change in skill at higher latitudes as a function of lead time. In agreement with previous analogous studies, results show that midlatitude GFS predictions tend to be improved in association with reducing tropical forecast errors during weeks 2-4, particularly over the North Pacific and western North America, where gains in subseasonal precipitation anomaly pattern correlations are substantial. It is also found that tropical nudging is more effective at improving NH subseasonal predictions in cases where skill is relatively low in the control reforecast, whereas it tends to improve less cases that are already relatively skillful. A time dependent analysis suggests a roughly one week lag between a decrease in tropical errors and an increase in NH predictive skill. The presentation will also include a combined tropical nudging and conditional skill analysis indicating that improved Madden Julian Oscillation (MJO) predictions throughout its lifecycle in the GFS could improve weeks 3-4 NH precipitation predictions.Webinar recording:
https://gmu.webex.com/gmu/ldr.php?RCID=0c6dcf8cc65849698f9dcffdd80df75b
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25 Apr
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Stratosphere Sub-Project 25 Apr, 23:06
23 Apr
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MJO and Teleconnections 23 Apr, 03:13
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Dear Colleagues,
Please join us for the April webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: Tropical origins of Weeks 2-4 forecasts errors during Northern Hemisphere cool season
Speaker: Juliana Dias, NOAA, Physical Sciences LaboratoryDate: Thursday, April 29, 2021
Time: 10:30am EST | 2:30pm UTCAbstract
A set of 30-day reforecast experiments is used to quantify the remote impacts of tropical forecast errors on the National Centers for Environmental Prediction (NCEP) global forecast system (GFS). The approach is to nudge the model towards reanalyses in the tropics and then measure the change in skill at higher latitudes as a function of lead time. In agreement with previous analogous studies, results show that midlatitude GFS predictions tend to be improved in association with reducing tropical forecast errors during weeks 2-4, particularly over the North Pacific and western North America, where gains in subseasonal precipitation anomaly pattern correlations are substantial. It is also found that tropical nudging is more effective at improving NH subseasonal predictions in cases where skill is relatively low in the control reforecast, whereas it tends to improve less cases that are already relatively skillful. A time dependent analysis suggests a roughly one week lag between a decrease in tropical errors and an increase in NH predictive skill. The presentation will also include a combined tropical nudging and conditional skill analysis indicating that improved Madden Julian Oscillation (MJO) predictions throughout its lifecycle in the GFS could improve weeks 3-4 NH precipitation predictions.To participate send and email to cstan at gmu.edu
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26 Mar
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MJO and Teleconnections 26 Mar, 00:03
25 Mar
26 Feb
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Dear Colleagues,
After a month of hiatus, we are resuming the monthly series of webinars hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project. Please join us for the August webinar.
Title: Impact of MJO propagation and background flow variability on the evolution of the MJO mid-latitude teleconnection
Speaker: Prof. Edmund Chang, School of Marine and Atmospheric Sciences, Stony Brook University
Date: Thursday, August 27, 2020
Time: 1pm EDT | 5pm UTCAbstract
The MJO acts as a tropical heat source to excite Rossby waves that propagate into the mid-latitudes and modulate the mid-latitude circulation and weather. In this talk, using results from idealized model experiments, I will examine how the MJO excited mid-latitude teleconnection may depend on the history of the MJO evolution, as well as how different mid-latitude large-scale background flow may impact the evolution of the MJO mid-latitude teleconnection.To participate send and email to subseasonal_to_seasonal_prediction_mjo_tel.
Webinar recording:
https://gmu.webex.com/recordingservice/sites/gmu/recording/playback/569c57769c04466eba33d1d2abf83643 -
Dear Colleagues,
We are resuming the monthly series of webinars hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project. Please join us for the January webinar.
Title: Intrinsic Uncertainty in the Euro-Atlantic Response to the MJO heating in boreal winter: Ongoing Results from ECMWF Re-Forecasts
Speaker: David Straus, George Mason UniversityDate: Thursday, January 28, 2021
Time: 10:30am EST | 3:30pm UTCAbstract
While the Euro-Atlantic response to the MJO has been well studied in reanalysis and a hierarchy of models, a factor that is often overlooked is the uncertainty in the response due to the intrinsic variability in the full diabatic heating during even a single phase of the MJO.
We examine the heating variability within large (51-member) ensembles of boreal winter reforecasts from the ECMWF model, focusing on forecasts initialized in phases 2 and 3 of the MJO (with heating anomalies located over the Indian Ocean). Results will be shown from new experimental reforecasts in which all the ensemble members utilize identical initial conditions, with the only difference between ensemble members arising from the application of stochastic physics in the target Indian Ocean region. (The stochastic physics is turned off outside the target region.)
The resulting uncertainty (ensemble spread) in the Euro-Atlantic response during the first few weeks of the forecasts is also examined, as well as some discussion of ongoing work to link the response uncertainties to those in the heating. The Euro-Atlantic response is seen to be similar to the traditional MJO response early in the forecast (MJO phases 2/3 leading to the NAO+ regime). However, later on in the forecast variability in the heating over the Pacific Ocean may play a role. Further experiments are planned to clarify the roles of ENSO vis-à-vis those of the MJO.Webinar recording:
https://gmu.webex.com/gmu/ldr.php?RCID=2aa2cd26f8ab42b18eef886e5ce34cd8 -
Dear Colleagues,
Please join us for the February webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: Mapping Large-scale Climate Variability to Hydrological Extremes: An Application of the Linear Inverse Model to Subseasonal Prediction
Speaker: Kai-Chih Tseng, GFDLDate: Thursday, February 25, 2021
Time: 10:30am EST | 3:30pm UTCAbstract
The excitation of the Pacific-North American (PNA) teleconnection pattern by the Madden-Julian Oscillation (MJO) has been considered as one of the most important predictability sources on subseasonal timescales over the extratropical Pacific and North America. However, until recently, the interactions between tropical heating and other extratropical modes and their relationships to subseasonal prediction have received comparatively little attention. In this study, a linear inverse model (LIM) is applied to examine the tropical-extratropical interactions. The LIM provides a means of calculating the response of a dynamical system to a small forcing by constructing a linear operator from the observed covariability statistics of the system. Given the linear assumptions, it is shown that the PNA is one of a few leading modes over the extratropical Pacific that can be strongly driven by tropical convection while other extratropical modes present at most a weak interaction with tropical convection. In the second part of this study, a two-step linear regression is introduced which leverages a LIM and large-scale climate variability to the prediction of hydrological extremes (e.g. atmospheric rivers) on subseasonal timescales. Consistent with the findings of the first part, most of the predictable signals on subseasonal timescales are determined by the dynamics of MJO-PNA teleconnection while other extratropical modes are important only at the shortest forecast leads.Webinar recording:
https://gmu.webex.com/gmu/ldr.php?RCID=48afbbc7b5324ac9b40ebfc1c8a3523c -
Dear Colleagues,
Please join us for the February webinar hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project.
Title: Mapping Large-scale Climate Variability to Hydrological Extremes: An Application of the Linear Inverse Model to Subseasonal Prediction
Speaker: Kai-ChihTseng, GFDLDate: Thursday, February 25, 2021
Time: 10:30am EST | 3:30pm UTCAbstract
The excitation of the Pacific-North American (PNA) teleconnection pattern by the Madden-Julian Oscillation (MJO) has been considered as one of the most important predictability sources on subseasonal timescales over the extratropical Pacific and North America. However, until recently, the interactions between tropical heating and other extratropical modes and their relationships to subseasonal prediction have received comparatively little attention. In this study, a linear inverse model (LIM) is applied to examine the tropical-extratropical interactions. The LIM provides a means of calculating the response of a dynamical system to a small forcing by constructing a linear operator from the observed covariability statistics of the system. Given the linear assumptions, it is shown that the PNA is one of a few leading modes over the extratropical Pacific that can be strongly driven by tropical convection while other extratropical modes present at most a weak interaction with tropical convection. In the second part of this study, a two-step linear regression is introduced which leverages a LIM and large-scale climate variability to the prediction of hydrological extremes (e.g. atmospheric rivers) on subseasonal timescales. Consistent with the findings of the first part, most of the predictable signals on subseasonal timescales are determined by the dynamics of MJO-PNA teleconnection while other extratropical modes are important only at the shortest forecast leads.Webinar recording:
https://gmu.webex.com/gmu/ldr.php?RCID=48afbbc7b5324ac9b40ebfc1c8a3523c
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25 Feb
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Forecast Verification Products and Development/R2O 25 Feb, 12:21
06 Feb
29 Jan
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MJO and Teleconnections 29 Jan, 04:53
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Dear Colleagues,
We are resuming the monthly series of webinars hosted by the WWRP/WCRP/S2S/MJO-Teleconnections sub-project. Please join us for the January webinar.
Title: Intrinsic Uncertainty in the Euro-Atlantic Response to the MJO heating in boreal winter: Ongoing Results from ECMWF Re-Forecasts
Speaker: David Straus, George Mason UniversityDate: Thursday, January 28, 2021
Time: 10:30am EST | 3:30pm UTCAbstract
While the Euro-Atlantic response to the MJO has been well studied in reanalysis and a hierarchy of models, a factor that is often overlooked is the uncertainty in the response due to the intrinsic variability in the full diabatic heating during even a single phase of the MJO.
We examine the heating variability within large (51-member) ensembles of boreal winter reforecasts from the ECMWF model, focusing on forecasts initialized in phases 2 and 3 of the MJO (with heating anomalies located over the Indian Ocean). Results will be shown from new experimental reforecasts in which all the ensemble members utilize identical initial conditions, with the only difference between ensemble members arising from the application of stochastic physics in the target Indian Ocean region. (The stochastic physics is turned off outside the target region.)
The resulting uncertainty (ensemble spread) in the Euro-Atlantic response during the first few weeks of the forecasts is also examined, as well as some discussion of ongoing work to link the response uncertainties to those in the heating. The Euro-Atlantic response is seen to be similar to the traditional MJO response early in the forecast (MJO phases 2/3 leading to the NAO+ regime). However, later on in the forecast variability in the heating over the Pacific Ocean may play a role. Further experiments are planned to clarify the roles of ENSO vis-à-vis those of the MJO.Webinar recording:
Webex meeting recording: S2S MJO-Teleconnections Monthly Webinar-20210128 1535-1
https://gmu.webex.com/gmu/ldr.php?RCID=2aa2cd26f8ab42b18eef886e5ce34cd8
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04 Dec 2020
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Machine Learning 04 Dec, 00:37 2020
01 Dec 2020
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Stratosphere Sub-Project 01 Dec, 01:39 2020
Dear Colleagues,
Please join us for the August webinar hosted by the WWRP/WCRP/S2S/MJO and Teleconnections sub-project.
Title: Predictability of Sahelian heatwaves and importance of tropical modes of variability
Speaker: Guigma Kiswendsida, Red Cross Red Crescent Climate Center
Date: Thursday, August 26, 2021
Time: 1:00pm EDT | 5:00pm UTC
Abstract
Heatwaves are a growing threat to human health worldwide, but remain poorly documented over Africa. This study addresses the predictability of Sahelian heatwaves during the February-March and April to June seasons as well as their large-scale drivers, with a focus on the role of the Madden-Julian Oscillation (MJO), the equatorial Rossby (ER) and Kelvin (EK) waves. The ECMWF ENS extendedrange forecasting system (ENS-ext), with a forecast horizon of 46 days, is used for the prediction skill assessment, the ERA5 reanalysis being the main reference dataset. Heatwaves are defined as spells of three or more consecutive days, where a given thermal index exceeds both the 75th percentile of its total distribution and the 90th percentile of its calendar day distribution. Tropical modes are obtained through a wavenumber-frequency decomposition of OLR anomalies.
The results show that ENS-ext is able to predict heatwaves with relatively good skill out to two to three weeks ahead. The highest forecast scores are obtained for daytime heatwaves and for the shortest leadtimes. With increasing lead-times, heatwaves become more predictable at nighttime than at daytime. Likewise, the prediction skill is initially higher during the February-March season for the shortest leadtimes, whereas for week 2 of the forecast and beyond, the April to June season heatwaves have a better predictability.
Tropical modes significantly affect the occurrence of heatwaves in the Sahel. Depending on their convective phase, they can either increase or decrease their probability. The MJO has the greatest effect, closely followed by the ER wave whereas the EK wave is less important to heatwave occurrence.
The observed relationship between heatwave occurrence and tropical mode activity is relatively well simulated by ENS-ext. The heatwave prediction skill is also found to be higher when the MJO and the ER wave are predicted to be active than when they are predicted to be inactive. Whilst this gain in prediction skill is limited to the first week of forecast for the ER wave, it extends out to the third week for the MJO.
Therefore, improving the representation of tropical modes in models will positively impact heatwave prediction at the subseasonal scale in the Sahel, and gain more time and precision for anticipatory actions.
If you would like to attend the webinar, please email to cstan AT gmu DOT edu
Recording of presentation:
https://docs.google.com/presentation/d/1ABqtjVGczf_oXxc8BlGsYh6kppjrQF06/edit?usp=sharing&ouid=101993203456660376262&rtpof=true&sd=true