The assimilation of SSM/I and TMI rainfall rates in the ECMWF 4D‐Var system

Mahfouf, Jean‐François; Bauer, Péter; Marécal, Virginie

doi:10.1256/qj.04.17

Cited by 30 publications

(18 citation statements)

References 42 publications

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“…There might be a contribution by data assimilated from the few radiosonde sites in the tropical Southern Hemisphere to the wave representation in ECMWF, but to a certain degree we can estimate that the wave structure in the analysis and forecast fields relies on model information rather than assimilation. Temperature and humidity data are assimilated in ECMWF, which helps the model moist physics to produce a rain rate closer to an observed value (Mahfouf et al 2005). Thus, we can assume that the forcing of the wave, which is latent heat release in convection, is resolved by the ECMWF model, but the vertical resolution in the stratosphere is not fine enough to have an accurate representation of the vertical structure of the wave.…”

Section: Discussionmentioning

confidence: 99%

Model Study of Intermediate-Scale Tropical Inertia–Gravity Waves and Comparison to TWP-ICE Campaign Observations

Evan

Alexander

Dudhia

2012

Journal of the Atmospheric Sciences

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A 2-day inertia-gravity wave (IGW) was observed in high-resolution radiosonde soundings of horizontal wind and temperature taken during the 2006 Tropical Warm Pool-International Cloud Experiment (TWP-ICE) experiment in the Darwin area. The wave was observed in the stratosphere above Darwin from 28 January to 5 February. A similar wave event is observed in the European Centre for Medium-Range Weather Forecasts (ECMWF) operational data. A comparison between the characteristics of the IGW derived with the ECMWF data to the properties of the wave derived with the radiosonde data shows that the ECMWF data capture similar structure for this 2-day wave event but with a larger vertical wavelength.A reverse ray-tracing method is used to localize the source region. Using ECMWF data to define the atmospheric background conditions and wave properties observed in the soundings, it is found that the 2-day wave event originated from deep convection in the Indonesian region around 20 January.The Weather Research and Forecasting (WRF) modeling system is used to complement the ECMWF data to assess the influence of vertical resolution and initial conditions on the wave structure. The model domain is configured as a tropical channel and the ECMWF analyses provide the north/south boundaries and initial conditions. WRF is used with the same horizontal resolution (40 km) as the operational ECMWF in 2006 while using a finer vertical grid spacing than ECMWF. The model is run from 18 January to 11 February to cover the wave life cycle. Different experiments are also performed to determine the sensitivity of the wave structure to cumulus schemes, initial conditions, and vertical resolution. The 2-day wave properties resulting from the WRF experiments are compared to those retrieved from the radiosonde data and from the ECMWF analyses. It is demonstrated that higher vertical resolution would be required for ECMWF to accurately resolve the vertical structure of the wave and its effect on the middle-atmospheric circulation.

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Section: Discussionmentioning

confidence: 99%

Model Study of Intermediate-Scale Tropical Inertia–Gravity Waves and Comparison to TWP-ICE Campaign Observations

Evan

Alexander

Dudhia

2012

Journal of the Atmospheric Sciences

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“…This topic has received considerable attention in recent years owing to the valuable information content contained in microwave observations that increases forecast skill (e.g., English et al 2000;Mahfouf et al 2005;Weng et al 2007;Kelly et al 2008). This topic has received considerable attention in recent years owing to the valuable information content contained in microwave observations that increases forecast skill (e.g., English et al 2000;Mahfouf et al 2005;Weng et al 2007;Kelly et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Uncertainties in Microwave Properties of Frozen Precipitation: Implications for Remote Sensing and Data Assimilation

Kulie

Bennartz

Greenwald

et al. 2010

Journal of the Atmospheric Sciences

128

163

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A combined active/passive modeling system that converts CloudSat observations to simulated microwave brightness temperatures (T B ) is used to assess different ice particle models under precipitating conditions. Simulation results indicate that certain ice models (e.g., low-density spheres) produce excessive scattering and implausibly low simulated T B s for stratiform precipitation events owing to excessive derived ice water paths (IWPs), while other ice models produce unphysical T B depressions due to the combined effects of elevated derived IWP and excessive particle size distribution-averaged extinction. An ensemble of nonspherical ice particle models, however, consistently produces realistic results under most circumstances and adequately captures the radiative properties of frozen hydrometeors associated with precipitation-with the possible exception of very high IWP events. Large derived IWP uncertainties exceeding 60% are also noted and may indicate IWP retrieval accuracy deficiencies using high-frequency passive microwave observations. Simulated T B uncertainties due to the ice particle model ensemble members approach 9 (5) K at 89 (157) GHz for high ice water path conditions associated with snowfall and ;2-3 (;1-2) K under typical stratiform rain conditions. These uncertainties, however, display considerable variability owing to ice water path, precipitation type, satellite zenith angle, and frequency. Comparisons between 157-GHz simulations and observations under precipitating conditions produce low biases (,1.5 K) and high correlations, but lower-frequency channels display consistent negative biases of 3-4 K in precipitating regions. Sample error correlations and covariance matrices for select microwave frequencies also show strong functional relationships with ice water path and variability depending on precipitation type.

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“…Wernli & Davies 1997;Wernli et al 2002), is associated with the presence of cloud. In order to make use of satellite data in rainy areas as well, the existing ECMWF 4D-Var system has recently been extended: first, model temperature and humidity profiles are adjusted by assimilating rain rates in 1D-Var; second, 1D-Var estimates of total column water vapour are assimilated in 4D-Var (Marécal & Mahfouf 2002;Mahfouf et al 2003). This revised 4D-Var assimilation scheme, which is going to become operational at ECMWF in 2005, might significantly increase the value of satellite data for severe storm prediction in Europe.…”

Section: Discussionmentioning

confidence: 99%

Reanalysis and reforecast of three major European storms of the twentieth century using the ECMWF forecasting system. Part I: Analyses and deterministic forecasts

2004

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In Part I of this study recent versions of the ECWMF Integrated Forecasting System (IFS) are used together with historical observational data to carry out reanalyses and deterministic reforecasts of three major north-west European wind storms of the twentieth century. The storms considered are the Dutch storm of 1 February 1953, the Hamburg storm of 17 February 1962, and the British October storm of 1987 (Great October Storm). Common to all these storms is their severity, which caused large loss of life and widespread damage. Reanalysis of the storms is based on a 3D-Var and 4D-Var assimilation scheme at a horizontal resolution of T L 159 (≈125 km) and T L 511 (≈50 km), respectively. Similarly, two different horizontal resolutions (T L 159 and T L 511) are used to investigate the deterministic predictability of these storms. The lower-resolution system is exactly that used in the ERA-40 reanalysis project. The high-resolution system is a more recent version of the ECMWF IFS.It is shown that the basic characteristics of the Dutch and Hamburg storms that gave rise to the storm surge are well predicted by the single deterministic forecasts up to about 48 and 84 hours, respectively, in advance.Our capability to predict the Great October Storm is more difficult to assess. On the one hand, even recent versions of the ECMWF IFS underestimate the severity of the storm in the very short-range (12-24-hour forecasts started at 12 UTC 15 October 1987). On the other hand, the high-resolution version of the ECMWF IFS provides excellent deterministic forecasts of the track and intensity of the storm up to 96 hours in advance. However, there are errors in the timing of the storm (12 hours for the 96 hour forecast).From the results presented in this study it is concluded -bearing in mind the limited number of cases considered -that with the current ECMWF forecasting system reliable deterministic predictions of some European wind storms are possible several days in advance.

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The assimilation of SSM/I and TMI rainfall rates in the ECMWF 4D‐Var system

Cited by 30 publications

References 42 publications

Model Study of Intermediate-Scale Tropical Inertia–Gravity Waves and Comparison to TWP-ICE Campaign Observations

Model Study of Intermediate-Scale Tropical Inertia–Gravity Waves and Comparison to TWP-ICE Campaign Observations

Uncertainties in Microwave Properties of Frozen Precipitation: Implications for Remote Sensing and Data Assimilation

Reanalysis and reforecast of three major European storms of the twentieth century using the ECMWF forecasting system. Part I: Analyses and deterministic forecasts

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