A Data Set for Intercomparing the Transient Behavior of Dynamical Model‐Based Subseasonal to Decadal Climate Predictions

Saurral, Ramiro Ignacio; Merryfield, William J.; Tolstykh, M. A.; Lee, Woo‐Sung; Doblas‐Reyes, Francisco J.; Garcı́a-Serrano, Javier; Massonnet, François; Meehl, Gerald A.; Teng, Haiyan

doi:10.1029/2021ms002570

Cited by 5 publications

(1 citation statement)

References 75 publications

(116 reference statements)

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“…To ensure our results are not specific to a single forecasting system, which is key to solving wider model error issues (Saurral et al, 2021), we expand it to other seasonal forecast systems from ECMWF, DWD, CMCC, and Meteo France. We found a similar tropical rainfall rate bias present in all four seasonal forecast systems (Figure 4) and these closely resembled the bias in GloSea that was shown in Figure 2a.…”

Section: Other Seasonal Forecast Systemsmentioning

confidence: 99%

Tropical Atlantic rainfall drives bias in extratropical seasonal forecasts

Collier,

Kettleborough,

Scaife

et al. 2023

Atmospheric Science Letters

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We investigate the impact of seasonal forecast biases in the Tropical Atlantic on the North Atlantic. The analysis uses a novel ensemble‐based method to estimate the impact of tropical rainfall bias on forecasts of the Extratropical North Atlantic. The inter‐ensemble spread of the forecast model is used to estimate the impact of the bias in Tropical Atlantic rainfall on the North Atlantic by selecting model members that happen to produce forecast anomalies that most closely resemble the tropical rainfall bias and using these as a proxy for the model error. The Tropical Atlantic rainfall bias impacts Rossby wave sources over the Subtropical Atlantic and there is a clear Rossby wave pattern originating from this area which is comparable to the mean bias in hindcasts. We argue that Tropical Atlantic rainfall errors explain a significant amount of the bias in seasonal forecasts over the Extratropical North Atlantic.

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Section: Other Seasonal Forecast Systemsmentioning

confidence: 99%

Tropical Atlantic rainfall drives bias in extratropical seasonal forecasts

Collier,

Kettleborough,

Scaife

et al. 2023

Atmospheric Science Letters

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Boreal winter stratospheric climatology in EC-EARTH: CMIP6 version

et al. 2022

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The performance of the European Consortium Earth-system model (EC-EARTH) in the boreal winter stratosphere is comprehensively assessed for the first time, in particular its version 3.3 that contributes to CMIP6. A 100-year long simulation with prescribed climatological boundary conditions and fixed radiative forcing, representative of present-day climate, is used to evaluate the simulation of the climatological stratospheric circulation and to identify model biases. Results show that EC-EARTH has a large issue with the vertical distribution of stratospheric temperature from the tropics to mid-latitudes, seemingly linked to radiative processes of ozone, leading to a biased warm middle-upper stratosphere. Associated with this model bias, EC-EARTH simulates a stronger polar vortex at upper-stratospheric levels while the Brewer-Dobson circulation at middle/lower levels is weaker than reanalysis. The amplitude of the climatological planetary waves is overall underestimated, but the magnitude of the background wave injection from the troposphere into the stratosphere is overestimated, related to a weaker polar vortex at lower-stratospheric levels and, thus, a less effective wave filtering. This bias in the westerly flow could have a contribution from parameterized waves. The overestimation of background wave driving is maximum in early-winter, and may explain the overestimated frequency of sudden stratospheric warmings at this time, as compared to reanalysis. The spatial distribution of wave injection climatology has revealed a distinctive role of the climatological planetary waves: while large-scale waves (wavenumbers 1–2) dominate the eddy heat flux over the North Pacific, small-scale waves (wavenumbers 3–4) are responsible for the doubled-lobe structure of the eddy heat flux over Eurasia. EC-EARTH properly simulates this climatological feature, although overestimates its amplitude over central Eurasia.

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Evaluating skill in predicting the Interdecadal Pacific Oscillation in initialized decadal climate prediction hindcasts in E3SMv1 and CESM1 using two different initialization methods and a small set of start years

Meehl,

Kirtman,

Glanville

et al. 2023

Clim Dyn

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It is a daunting challenge to conduct initialized hindcasts with enough ensemble members and associated start years to form a drifted climatology from which to compute the anomalies necessary to quantify the skill of the hindcasts when compared to observations. This limits the ability to experiment with case studies and other applications where only a few initial years are needed. Here we run a set of hindcasts with CESM1 and E3SMv1 using two different initialization methods for a limited set of start years and use the respective uninitialized free-running historical simulations to form the model climatologies. Since the drifts from the observed initial states in the hindcasts toward the uninitialized model state are large and rapid, after a few years the drifted initialized models approach the uninitialized model climatological errors. Therefore, hindcasts from the limited start years can use the uninitialized climatology to represent the drifted model states after about lead year 3, providing a means to compute forecast anomalies in the absence of a large hindcast sample. There is comparable skill for predicting spatial patterns of multi-year Pacific sea surface temperature anomalies in the domain of the Interdecadal Pacific Oscillation using this method compared to the conventional methodology with a large hindcast data set, though there is a model dependence to the drifts in the two initialization methods.

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A Data Set for Intercomparing the Transient Behavior of Dynamical Model‐Based Subseasonal to Decadal Climate Predictions

Cited by 5 publications

References 75 publications

Tropical Atlantic rainfall drives bias in extratropical seasonal forecasts

Tropical Atlantic rainfall drives bias in extratropical seasonal forecasts

Boreal winter stratospheric climatology in EC-EARTH: CMIP6 version

Evaluating skill in predicting the Interdecadal Pacific Oscillation in initialized decadal climate prediction hindcasts in E3SMv1 and CESM1 using two different initialization methods and a small set of start years

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