Influence of the North American Monsoon Experiment (NAME) 2004 Enhanced Soundings on NCEP Operational Analyses

2007 ◽  
Vol 20 (9) ◽  
pp. 1821-1842 ◽  
Author(s):  
Kingtse C. Mo ◽  
Eric Rogers ◽  
Wesley Ebisuzaki ◽  
R. Wayne Higgins ◽  
J. Woollen ◽  
...  
Keyword(s):  
Data Assimilation ◽  
North American ◽  
Gulf Of California ◽  
North American Monsoon ◽  
Climate Data ◽  
Regional Data ◽  
Low Level ◽  
Low Level Jet ◽  
Data Assimilation System ◽  
Assimilation System

Abstract During the 2004 North American Monsoon Experiment (NAME) field campaign, an extensive set of enhanced atmospheric soundings was gathered over the southwest United States and Mexico. Most of these soundings were assimilated into the NCEP operational global and regional data assimilation systems in real time. This presents a unique opportunity to carry out a series of data assimilation experiments to examine their influence on the NCEP analyses and short-range forecasts. To quantify these impacts, several data-withholding experiments were carried out using the global Climate Data Assimilation System (CDAS), the Regional Climate Data Assimilation System (RCDAS), and the three-dimensional variational data assimilation (3DVAR) Eta Model Data Assimilation System (EDAS) for the NAME 2004 enhanced observation period (EOP). The impacts of soundings vary between the assimilation systems examined in this study. Overall, the influence of the enhanced soundings is concentrated over the core monsoon area. While differences at upper levels are small, the differences at lower levels are more substantial. The coarse-resolution CDAS does not properly resolve the Gulf of California (GoC), so the assimilation system is not able to exploit the additional soundings to improve characteristics of the Gulf of California low-level jet (GCLLJ) and the associated moisture transport in the GoC region. In contrast, the GCLLJ produced by RCDAS is conspicuously stronger than the observations, though the problem is somewhat alleviated with additional special NAME soundings. For EDAS, soundings improve the intensity and position of the Great Plains low-level jet (GPLLJ). The soundings in general improve the analyses over the areas where the assimilation system has the largest uncertainties and errors. However, the differences in regional analyses owing to the soundings are smaller than the differences between the two regional data assimilation systems.

scholarly journals The Impact of High-Resolution SALLJEX Data on Global NCEP Analyses

2007 ◽  
Vol 20 (23) ◽  
pp. 5765-5783 ◽  
Author(s):  
Dirceu L. Herdies ◽  
Vernon E. Kousky ◽  
Wesley Ebisuzaki
Keyword(s):  
Data Assimilation ◽  
Similar Data ◽  
Climate Data ◽  
Low Level ◽  
The Andes ◽  
Pilot Balloon ◽  
Low Level Jet ◽  
The Impact ◽  
Data Assimilation System ◽  
Assimilation System

Abstract A data assimilation study was performed to assess the impact of observations from the South American Low-Level Jet Experiment (SALLJEX) on analyses in the region east of the Andes Mountains from western Brazil to central Argentina. The Climate Data Assimilation Systems (CDAS)-1 and -2 and the Global Data Assimilation System (GDAS) were run with and without the additional SALLJEX rawinsondes and pilot balloon observations. The experiments for each data assimilation system revealed similar features, with a stronger low-level flow east of the Andes when SALLJEX data were included. GDAS had the strongest low-level jet (LLJ) when compared with observations. In the experiments that used additional rawinsonde and pilot balloon data, the LLJ was displaced westward in comparison to the analyses run without the SALLJEX data. The vertical structure of the meridional wind in the analyses was much closer to observed rawinsonde profiles in the experiments that included SALLJEX data than in the control experiments, and the results show that, although there are more pilot balloon observations than rawinsonde observations in the SALLJEX dataset, most of the improvements in the analyses can be obtained by only including rawinsonde observations. This was especially true for GDAS. The results of this study can serve as a benchmark for similar data impact studies using higher-resolution data assimilation systems.

The BMRC Regional Data Assimilation System

1990 ◽  
Vol 118 (6) ◽  
pp. 1217-1237 ◽  
Author(s):  
G. A. Mills ◽  
R. S. Seaman
Keyword(s):  
Data Assimilation ◽  
Regional Data ◽  
Data Assimilation System ◽  
Assimilation System

Simulations of the 2004 North American Monsoon: NAMAP2

2009 ◽  
Vol 22 (24) ◽  
pp. 6716-6740 ◽  
Author(s):  
D. S. Gutzler ◽  
L. N. Long ◽  
J. Schemm ◽  
S. Baidya Roy ◽  
M. Bosilovich ◽  
...  
Keyword(s):  
Boundary Conditions ◽  
North American ◽  
Warm Season ◽  
North American Monsoon ◽  
Regional Models ◽  
Global Models ◽  
Low Level ◽  
The Core ◽  
The North ◽  
Low Level Jet

Abstract The second phase of the North American Monsoon Experiment (NAME) Model Assessment Project (NAMAP2) was carried out to provide a coordinated set of simulations from global and regional models of the 2004 warm season across the North American monsoon domain. This project follows an earlier assessment, called NAMAP, that preceded the 2004 field season of the North American Monsoon Experiment. Six global and four regional models are all forced with prescribed, time-varying ocean surface temperatures. Metrics for model simulation of warm season precipitation processes developed in NAMAP are examined that pertain to the seasonal progression and diurnal cycle of precipitation, monsoon onset, surface turbulent fluxes, and simulation of the low-level jet circulation over the Gulf of California. Assessment of the metrics is shown to be limited by continuing uncertainties in spatially averaged observations, demonstrating that modeling and observational analysis capabilities need to be developed concurrently. Simulations of the core subregion (CORE) of monsoonal precipitation in global models have improved since NAMAP, despite the lack of a proper low-level jet circulation in these simulations. Some regional models run at higher resolution still exhibit the tendency observed in NAMAP to overestimate precipitation in the CORE subregion; this is shown to involve both convective and resolved components of the total precipitation. The variability of precipitation in the Arizona/New Mexico (AZNM) subregion is simulated much better by the regional models compared with the global models, illustrating the importance of transient circulation anomalies (prescribed as lateral boundary conditions) for simulating precipitation in the northern part of the monsoon domain. This suggests that seasonal predictability derivable from lower boundary conditions may be limited in the AZNM subregion.

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