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- Title
Comparison of Conventional and Constrained Variational Methods for Computing Large‐Scale Budgets and Forcing Fields.
- Authors
Ciesielski, Paul E.; Johnson, Richard H.; Tang, Shuaiqi; Zhang, Yunyan; Xie, Shaocheng
- Abstract
Analyses of atmospheric heat and moisture budgets serve as an effective tool to study convective characteristics over a region and to provide large‐scale forcing fields for various modeling applications. This paper examines two popular methods for computing large‐scale atmospheric budgets: the conventional budget method (CBM) using objectively gridded analyses based primarily on radiosonde data and the constrained variational analysis (CVA) approach which supplements vertical profiles of atmospheric fields with measurements at the top of the atmosphere and at the surface to conserve mass, water, energy, and momentum. Successful budget computations are dependent on accurate sampling and analyses of the thermodynamic state of the atmosphere and the divergence field associated with convection and the large‐scale circulation that influences it. Utilizing analyses generated from data taken during Dynamics of the Madden‐Julian Oscillation (DYNAMO) field campaign conducted over the central Indian Ocean from October to December 2011, we evaluate the merits of these budget approaches and examine their limitations. While many of the shortcomings of the CBM, in particular effects of sampling errors in sounding data, are effectively minimized with CVA, accurate large‐scale diagnostics in CVA are dependent on reliable background fields and rainfall constraints. For the DYNAMO analyses examined, the operational model fields used as the CVA background state provided wind fields that accurately resolved the vertical structure of convection in the vicinity of Gan Island. However, biases in the model thermodynamic fields were somewhat amplified in CVA resulting in a convective environment much weaker than observed. Plain Language Summary: Two popular methods for computing large‐scale atmospheric budgets are examined: the conventional budget method (CBM) using primarily sounding data (i.e., vertical profiles describing the state of the atmosphere) and the constrained variational analysis (CVA) approach which supplements sounding data with measurements at the top of the atmosphere and at the surface to conserve mass, water, energy, and momentum. Successful budget computations are dependent on accurate sampling and analyses of the thermodynamic state of the atmosphere and the wind field associated with convection and the large‐scale circulation that influences it. Utilizing analyses generated from data taken during Dynamics of the Madden‐Julian Oscillation (DYNAMO) field campaign conducted over the central Indian Ocean, we evaluate the merits of these budget approaches and examine their limitations. While many of the shortcomings of the CBM are effectively minimized with CVA, the success of the CVA approach is dependent on reliable background fields and rainfall constraints. Merits and limitations of both methods are summarized. Key Points: Merits and limitations of two methods for computing large‐scale atmospheric budgets are examinedConstrained variational analysis (CVA) method effectively minimizes many of the shortcomings of the conventional budget methodHowever, accurate large‐scale diagnostics in CVA are dependent on reliable background fields and rainfall constraints
- Subjects
TERRESTRIAL heat flow; ATMOSPHERIC temperature; MADDEN-Julian oscillation; OCEAN-atmosphere interaction; OSCILLATIONS
- Publication
Journal of Geophysical Research. Atmospheres, 2021, Vol 126, Issue 16, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2021JD035183