A Comparison of Tropical Precipitation Simulated by the Community Climate Model with That Measured by the Tropical Rainfall Measuring Mission Satellite (original) (raw)
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Journal of Applied Meteorology and Climatology, 2014
Forecasts of precipitation and water vapor made by the Met Office global numerical weather prediction (NWP) model are evaluated using products from satellite observations by the Special Sensor Microwave Imager/Sounder (SSMIS) and Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) for June–September 2011, with a focus on tropical areas (30°S–30°N). Consistent with previous studies, the predicted diurnal cycle of precipitation peaks too early (by ~3 h) and the amplitude is too strong over both tropical ocean and land regions. Most of the wet and dry precipitation biases, particularly those over land, can be explained by the diurnal-cycle discrepancies. An overall wet bias over the equatorial Pacific and Indian Oceans and a dry bias over the western Pacific warm pool and India are linked with similar biases in the climate model, which shares common parameterizations with the NWP version. Whereas precipitation biases develop within hours in the NWP m...
A Ten-Year Tropical Rainfall Climatology Based on a Composite of TRMM Products
Journal of the Meteorological Society of Japan, 2009
A new climatology of tropical surface rain is described based on a composite of ten years of precipitation retrievals and analyses from the Tropical Rainfall Measuring Mission (TRMM). This TRMM Composite Climatology (TCC) consists of a combination of selected TRMM rainfall products over both land and ocean. This new climatology will be useful as a summary of surface rain estimates from TRMM (not replacing the individual products) and should be useful as a ready comparison with other non-TRMM estimates and for comparison with calculated precipitation from general circulation models. The TCC mean precipitation for each calendar month and for the annual total is determined by a simple mean of the three chosen products (slightly different combination of products over land and ocean). Over ocean areas, the three TRMM products are those based on the passive microwave (2A12), radar (2A25) and combined retrievals (2B31). Over land, the multi-satellite product (3B43) is substituted for the passive microwave product. The standard deviation (σ) at each point among the three estimates gives a measure of dispersion, which can be used as an indicator of confidence and as an estimate of error. The mean annual precipitation over the TRMM domain of 35°N to 35°S in the new climatology is 2.68 mm d-1 (ocean and land combined) with a σ of .05 mm d-1 , or 2.0%. The ocean (land) value is 2.74 mm d-1 (2.54) with a σ/mean of 2.1% (5.4%). The larger dispersion (and assumed error) over land is due to the greater difficulty of satellite rain retrieval over land, especially with passive microwave techniques and especially in mountains and along coasts. The maps of σ and σ/mean indicate these regions of less confidence, including areas over the ocean such as the eastern Pacific Ocean. Examples of values for different latitude bands, seasonal variations, and relations of the individual inputs to the composite mean are given. Comparison with analyses from the Global Precipitation Climatology Project (GPCP) indicates lower values than GPCP for the TRMM composite in middle latitudes over the ocean and over northern Australia and India during their respective summer monsoons.
CMIP5 Simulations of Low-Level Tropospheric Temperature and Moisture over the Tropical Americas
Journal of Climate, 2013
Global warming has been linked to systematic changes in North and South America's climates and may severely impact the North American monsoon system (NAMS) and South American monsoon system (SAMS). This study examines interannual-to-decadal variations and changes in the low-troposphere (850 hPa) temperature (T850) and specific humidity (Q850) and relationships with daily precipitation over the tropical Americas using the NCEP-NCAR reanalysis, the Climate Forecast System Reanalysis (CFSR), and phase 5 of the Coupled Model Intercomparison Project (CMIP5) simulations for two scenarios: ''historic'' and high-emission representative concentration pathway 8.5 (RCP8.5). Trends in the magnitude and area of the 85th percentiles were distinctly examined over North America (NA) and South America (SA) during the peak of the respective monsoon season. The historic simulations and the two reanalyses agree well and indicate that significant warming has occurred over tropical SA with a remarkable increase in the area and magnitude of the 85th percentile in the last decade (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005). The RCP8.5 CMIP5 ensemble mean projects an increase in the T850 85th percentile of about 2.58C (2.88C) by 2050 and 4.88C (5.58C) over SA (NA) by 2095 relative to 1955. The area of SA (NA) with T850 $ the 85th percentile is projected to increase from ;10% (15%) in 1955 to ;58% (;33%) by 2050 and ;80% (;50%) by 2095. The respective increase in the 85th percentile of Q850 is about 3 g kg 21 over SAMS and NAMS by 2095. CMIP5 models project variable changes in daily precipitation over the tropical Americas. The most consistent is increased rainfall in the intertropical convergence zone in December-February (DJF) and June-August (JJA) and decreased precipitation over NAMS in JJA.
CMIP5 Simulations of Low-Level Tropospheric Temperature and Moisture over Tropical Americas
2013
Global warming has been linked to systematic changes in North and South America's climates and may severely impact the North American monsoon system (NAMS) and South American monsoon system (SAMS). This study examines interannual-to-decadal variations and changes in the low-troposphere (850 hPa) temperature (T850) and specific humidity (Q850) and relationships with daily precipitation over the tropical Americas using the NCEP-NCAR reanalysis, the Climate Forecast System Reanalysis (CFSR), and phase 5 of the Coupled Model Intercomparison Project (CMIP5) simulations for two scenarios: ''historic'' and high-emission representative concentration pathway 8.5 (RCP8.5). Trends in the magnitude and area of the 85th percentiles were distinctly examined over North America (NA) and South America (SA) during the peak of the respective monsoon season. The historic simulations (1951-2005) and the two reanalyses agree well and indicate that significant warming has occurred over tropical SA with a remarkable increase in the area and magnitude of the 85th percentile in the last decade (1996-2005). The RCP8.5 CMIP5 ensemble mean projects an increase in the T850 85th percentile of about 2.58C (2.88C) by 2050 and 4.88C (5.58C) over SA (NA) by 2095 relative to 1955. The area of SA (NA) with T850 $ the 85th percentile is projected to increase from ;10% (15%) in 1955 to ;58% (;33%) by 2050 and ;80% (;50%) by 2095. The respective increase in the 85th percentile of Q850 is about 3 g kg 21 over SAMS and NAMS by 2095. CMIP5 models project variable changes in daily precipitation over the tropical Americas. The most consistent is increased rainfall in the intertropical convergence zone in December-February (DJF) and June-August (JJA) and decreased precipitation over NAMS in JJA.
Effect of Tropical Nonconvective Condensation on Uncertainty in Modeled Projections of Rainfall
Journal of Climate, 2019
We find that part of the uncertainty in the amplitude and pattern of the modeled precipitation response to CO 2 forcing traces to tropical condensation not directly involved with parameterized convection. The fraction of tropical rainfall associated with large-scale condensation can vary from a few percent to well over half depending on model details and parameter settings. In turn, because of the coupling between condensation and tropical circulation, the different ways model assumptions affect the large-scale rainfall fraction also affect the patterns of the response within individual models. In two single-model ensembles based on the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM), versions 3.1 and 5.3, we find strong correlations between the fraction of tropical large-scale rain and both climatological rainfall and circulation and the response to CO 2 forcing. While the effects of an increasing tropical large-scale rain fraction are opposite in some ways in the two ensembles-for example, the Hadley circulation weakens with the large-scale rainfall fraction in the CAM3.1 ensemble while strengthening in the CAM5.3 ensemblewe can nonetheless understand these different effects in terms of the relationship between latent heating and circulation, and we propose explanations for each ensemble. We compare these results with data from phase 5 of the Coupled Model Intercomparison Project (CMIP5), for which some of the same patterns hold. Given the importance of this partitioning, there is a need for constraining this source of uncertainty using observations. However, since a ''large-scale rainfall fraction'' is a modeling construct, it is not clear how observations may be used to test various modeling assumptions determining this fraction.
Evaluation of climate simulations produced with the Brazilian global atmospheric model version 1.2
Climate Dynamics, 2020
This paper presents an evaluation of climate simulations produced by the Brazilian Global Atmospheric Model version 1.2 (BAM-1.2) of the Center for Weather Forecast and Climate Studies (CPTEC). The model was run over the 1975-2017 period at two spatial resolutions, corresponding to ~180 and ~100 km, both with 42 vertical levels, following most of the Atmospheric Model Intercomparison Project (AMIP) protocol. In this protocol, observed sea surface temperatures (SSTs) are used as boundary conditions for the atmospheric model. Four ensemble members were run for each of the two resolutions. A series of diagnostics was computed for assessing the model´s ability to represent the top of the atmosphere (TOA) radiation, atmospheric temperature, circulation and precipitation climatological features. The representation of precipitation interannual variability, El Niño-Southern Oscillation (ENSO) precipitation teleconnections, the Madden and Julian Oscillation (MJO) and daily precipitation characteristics was also assessed. The model at both resolutions reproduced many observed temperature, atmospheric circulation and precipitation climatological features, despite several identified biases. The model atmosphere was found to be more transparent than the observations, leading to misrepresentation of cloud-radiation interactions. The net cloud radiative forcing, which produces a cooling effect on the global mean climate at the TOA, was well represented by the model. This was found to be due to the compensation between both weaker longwave cloud radiative forcing (LWCRF) and shortwave cloud radiative forcing (SWCRF) in the model compared to the observations. The model capability to represent inter-annual precipitation variability at both resolutions was found to be linked to the adequate representation of ENSO teleconnections. However, the model produced weaker than observed convective activity associated with the MJO. Light daily precipitation over the southeast of South America and other climatologically similar regions was diagnosed to be overestimated, and heavy daily precipitation underestimated by the model. Increasing spatial resolution helped to slightly reduce some of the diagnosed biases. The performed evaluation identified model aspects that need to be improved. These include the representation of polar continental surface and sea ice albedo, stratospheric ozone, low marine clouds, and daily precipitation features, which were found to be larger and last longer than the observed features.
Diurnal cycle of precipitation simulated by RegCM4 over South America: present and future scenarios
Climate Research, 2016
The diurnal cycle of precipitation (DCP) is not the same in every region of the globe because it depends on the local dynamics and thermodynamics of each region. The main purpose of this study was to analyze the DCP simulated by the Regional Climate Model version 4 (RegCM4) nested in the HadGEM2-ES over South America in 3 time slices: historical (1998−2005), near (2020−2048), and far (2070−2098) future climates considering the austral summer and winter seasons. This work is part of the Phase I CORDEX RegCM4 hyper-Matrix (or CREMA) experiment and uses the RCP8.5 scenario for the future climate periods. The historical period is validated by comparing the simulation with the Tropical Rainfall Measuring Mission (TRMM-2A25 and TRMM-3B42 v7) and Global Satellite Mapping of Precipitation (GSMaP MVK+) datasets. The contrasts in the DCP between tropics and extratropics registered in TRMM and GSMaP are in general simulated by RegCM4. During summer, the model simulates the peak of precipitation at 18:00 UTC in the tropical and subtropical subdomains as in the satellite products. In winter, RegCM4 overestimates the precipitation in all subtropical subdomains, and the DCP is better simulated in the tropical region. Among the results for the future scenarios, in general, in summer the near future shows the DCP pattern and intensity to be similar to the present climate, while the far future indicates an increase in precipitation intensity between 03:00 and 12:00 UTC in 8 of the 12 subdomains analyzed.
Comparison of Precipitation Datasets over the Tropical South American and African Continents
Journal of Hydrometeorology, 2009
Six rainfall datasets are compared over the Amazon basin, Northeast Brazil, and the Congo basin. These datasets include three gauge-only precipitation products from the Climate Prediction Center (CPC), Global Precipitation Climatology Center (GPCC), and Brazilian Weather Forecast and Climate Studies Center (CLMNLS), and three combined gauge and satellite precipitation datasets from the CPC Merged Analysis of Precipitation (CMAP), Global Precipitation Climatology Project (GPCP), and Tropical Rainfall Measuring Mission (TRMM) product. The pattern of the annual precipitation is consistently represented by these data, despite the differences in methods and periods of averaging. Quantitatively, the differences in annual precipitation among these datasets are 5% more than the Amazon domain (0°–15°S, 50°–70°W), 22% more than Northeast Brazil (5°–10°S, 35°–45°W), and 11% more than the Congo domain (5°N–10°S, 15°–30°E). Over the Amazon domain the rainfall variation is well correlated between...