 |
| Titel |
Frequency of deep convective clouds in the tropical zone from 10 years of AIRS data |
| VerfasserIn |
H. H. Aumann, A. Ruzmaikin |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 21 ; Nr. 13, no. 21 (2013-11-07), S.10795-10806 |
| Datensatznummer |
250085795
|
| Publikation (Nr.) |
 copernicus.org/acp-13-10795-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
Deep convective clouds (DCCs) have been widely studied because of their
association with heavy precipitation and severe weather events. Changes
in the properties of DCCs are likely in a changing climate. Ten years of data
collected by Atmospheric Infrared Sounder (AIRS) allow us to identify
decadal trends in frequency of occurrence of DCCs over land and ocean. In the
past, DCCs have been identified in the thermal infrared by three methods: (1)
thresholds based on the absolute value of an atmospheric window channel
brightness temperature; (2) thresholds based on the difference between the
brightness temperature in an atmospheric window channel and the brightness
temperature centered on a strong water vapor absorption line; and (3) a
threshold using the difference between the window channel brightness
temperature and the tropopause temperature based on climatology.
Simultaneous observations of these infrared identified DCCs with the Advanced
Microwave Sounding Unit–Humidity Sounder for Brazil (AMSU-HSB) using 183 GHz water channels provide
a statistical correlation with microwave deep convection and overshooting
convection. In the past 10 years, the frequency of occurrence of DCCs
has decreased for the tropical ocean, while it has increased for tropical land. The
area of the tropical zone associated with DCCs is typically much less than
1%. We find that the least frequent, more extreme DCCs show the largest
trend in frequency of occurrence, increasing over land and decreasing over
ocean.
The trends for land and ocean closely balance, such that the DCC frequency
changed at an insignificant rate for the entire tropical zone. This pattern
of essentially zero trend for the tropical zone, but opposite land/ocean
trends, is consistent with measurements of global precipitation. The changes
in frequency of occurrence of the DCCs are correlated with the Niño34
index, which defines the sea surface temperature (SST) anomaly in the east-central Pacific. This is
also consistent with patterns seen in global precipitation. This suggests
that the observed changes in the frequency are part of a decadal variability
characterized by shifts in the main tropical circulation patterns, which
does not fully balance in the 10-year AIRS data record. The regional
correlations and anti-correlations of the DCC frequency anomaly with the
Multivariate ENSO Index (MEI) provide a new perspective for the regional
analysis of past events, since the SST anomaly in the Nino34 region is
available in the form of the extended MEI from 1871. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|