Momentum Budget Diagnosis and the Parameterization of Subgrid-Scale Orographic Drag in Global GRAPES
The initial tendency approach is used to diagnose systematic errors in global GRAPES （Global/Regional Assimilation Prediction System）, including overly strong westerlies in the northern midlatitudes, cold/warm bias dipoles in the vicinity of the tropopause, and excessively strong southerlies in down...
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| Published in | Acta meteorologica Sinica Vol. 30; no. 5; pp. 771 - 788 |
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| Main Author | |
| Format | Journal Article |
| Language | English |
| Published |
Beijing
The Chinese Meteorological Society
01.08.2016
Numerical Weather Prediction Center of the China Meteorological Administration, Beijing 100081 National Meteorological Center, Beijing 100081 |
| Subjects | |
| Online Access | Get full text |
| ISSN | 2095-6037 0894-0525 2198-0934 2191-4788 |
| DOI | 10.1007/s13351-016-6033-y |
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| Summary: | The initial tendency approach is used to diagnose systematic errors in global GRAPES （Global/Regional Assimilation Prediction System）, including overly strong westerlies in the northern midlatitudes, cold/warm bias dipoles in the vicinity of the tropopause, and excessively strong southerlies in downstream regions of the Tibetan Plateau. This approach, involving the use of the assimilation system, focuses on the first few time steps of numerical weather forecasts to identify the deficiencies in diabatic forcing. The results show that there is insufficient diabatic dissipation in the upper troposphere and lower stratosphere of the northern midlatitudes and the lower troposphere of most latitudes, which results from the absence of a parameterization of subgrid orographic drag in global GRAPES. A scheme to parameterize the effects of these drags is therefore tested and the experiments indicate that the newly introduced scheme reduces zonal momentum budget residuals, weakens the northern midlatitude westerlies and southerlies in the downstream regions of the Tibetan Plateau, decreases the cold/warm bias dipoles, and leads to improved objective verification scores. |
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| Bibliography: | momentum budget diagnosis, initial tendency approach, gravity-wave drag, blocked-flow drag 11-2277/P The initial tendency approach is used to diagnose systematic errors in global GRAPES （Global/Regional Assimilation Prediction System）, including overly strong westerlies in the northern midlatitudes, cold/warm bias dipoles in the vicinity of the tropopause, and excessively strong southerlies in downstream regions of the Tibetan Plateau. This approach, involving the use of the assimilation system, focuses on the first few time steps of numerical weather forecasts to identify the deficiencies in diabatic forcing. The results show that there is insufficient diabatic dissipation in the upper troposphere and lower stratosphere of the northern midlatitudes and the lower troposphere of most latitudes, which results from the absence of a parameterization of subgrid orographic drag in global GRAPES. A scheme to parameterize the effects of these drags is therefore tested and the experiments indicate that the newly introduced scheme reduces zonal momentum budget residuals, weakens the northern midlatitude westerlies and southerlies in the downstream regions of the Tibetan Plateau, decreases the cold/warm bias dipoles, and leads to improved objective verification scores. CHEN qiying1,2, SHEN Xueshun1,2 , SUN Jian1,2 ,LIU Kun1,2（ 1 National Meteorological Center, Beijing 100081 2 Numerical Weather Prediction Center of the China Meteorological Administration, Beijing 100081） ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
| ISSN: | 2095-6037 0894-0525 2198-0934 2191-4788 |
| DOI: | 10.1007/s13351-016-6033-y |