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- Title
Understanding the ACCESS model errors over the Maritime Continent using CloudSat and CALIPSO simulators.
- Authors
Nguyen, Hanh; Franklin, Charmaine; Protat, Alain
- Abstract
Precipitation and cloud properties from the Australian Community Climate and Earth System Simulator ( ACCESS1.3) atmospheric model are evaluated over the Maritime Continent during the monsoon season using satellite observations. The model rainfall errors in December-February are characterized by a wet bias east of 120°E and a dry bias west of that longitude. A closer look at the complex land-sea composition of the Maritime Continent reveals that ACCESS1.3 overestimates rainfall over the islands and underestimates it in the surrounding waters. These rainfall biases are associated with a distinct low-level convergence bias over land, a divergence bias over ocean, and a high-level cloud fraction overestimate over land and ocean. The complementary information offered by CloudSat and CALIPSO evaluations further shows that the model overestimates high- and low-level cloudiness and light rain and drizzle but underestimates the occurrence of mid-level clouds. Sensitivity tests are carried out to study the model response to physics parametrizations to understand these model errors. In particular, modifications to the existing parametrization such as changes to the convection scheme, to the rainfall characteristics or to the circulation, appear to qualitatively help reduce model errors. These results show that rainfall and high-level cloud fraction can be improved, but the model still suffers from a lack of occurrence of hydrometeors in the mid-levels in all sensitivity tests. Increasing cloudiness and moisture in the low- and mid-levels may be crucial to generating deeper convection and higher ice water content in the model.
- Subjects
ATMOSPHERIC models; METEOROLOGICAL precipitation; CLOUD forecasting; CONVERGENCE (Meteorology); CLOUDINESS; ATMOSPHERIC circulation
- Publication
Quarterly Journal of the Royal Meteorological Society, 2017, Vol 143, Issue 709, p3136
- ISSN
0035-9009
- Publication type
Article
- DOI
10.1002/qj.3168