Mesoscale Convective Systems (MCS) in equatorial Indian and Pacific Ocean
Collaborators: Brian Mapes (RSMAS/MPO, Miami, FL) and David Long (MERS/BYU, Salt Lake City, UT).
The detection and formation of "Mesoscale Convective Systems" (MCS) in the equatorial regions of the Indian
and Pacific Oceans are examined by using several satellite data sets, including:
- wind and rain estimates from QSCAT, including experimental scatterometer data of simultaneous
wind and rain retrievals, as well as ultra high-resolution data (2.5x2.5km) from David Long at BYU;
- SST from TMI;
- precipitable water (PW) from RSS; and
- cloud top temperature from CLAUS.
Equatorial regions of interest are:
- Pacifc Ocean, 130° - 180°E, 0° - 30°N.
- Indian Ocean, 50° - 95°E, 30°S - 10°N.
Click on images for enlarged versions of plots.
1. Cloud Top Temperature Data (CLAUS)
CLAUS, from the "Cloud Archive User Service" , is a
brightness temperature dataset, and is a proxy for the temperature of the emitting surface.
It is calculated from upwelling IR, so it represents clouds - the colder the higher, similar to OLR in that respect.
CLAUS data are used to identify MCS systems. The data are available globally, 3-hourly, and at a resolution of
0.5° x 0.5° (Jan 1999 - June 2005).
Local temperature minima are determined by smoothing the data over a 3.5°x3.5° area
(by weighted averaging - highest weight at center and decreasing linearly to edges of the 7x7 point
area). Locations are saved when local temperature minima are &le 290°. Examples of cloud temperature
maps are presented below for two different times.
Fig. 1.1 Cloud top temperature (CLAUS), on 1/30/2000 9:00hr, (a) not smoothed, and
(b) 3.5°x3.5° smoothed. Local minima with T &le 270° are marked with +, and
T &le 270° with &oplus .
Fig. 1.2 Cloud top temperature (CLAUS), on 1/31/2000 3:00hr, (a) not smoothed, and
(b) 3.5°x3.5° smoothed.
The number of identified temperature minima are displayed in the next plot for the entire year 2000,
for each ocean.
The temperature thresholds are 220°, 250°, 270°, and 290°. The 220° total for the Pacific Ocean
in 2000 is N = 3,847, or about 10 per day.
Fig. 1.3 Number of temperature minima in each 3-hourly field of year 2000, for equatorial (a) Pacific Ocean, and
(b) Indian Ocean.
Wind speed histogram for BYU ultra hi-res QSCAT retrievals are shown below for 12 revs in the area of
interest in the western equatorial Pacific Ocean. In these revs, at least one MCS system with cloud top
temperatures &le 220°K are present. Most of the revs depict Pacific typhoons. All WVC within
6 grid cells of land-flagged WVC have been excluded from the histogram calculation.
Fig. 1.4 QSCAT wind speed histogram, BYU ultra hi-res revs, during time period
1/30-9/9/2000, 12 revs from rev 3202-6373, coastal wvc not included.
last modified on May 25, 2007
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