TITLE:
Assessment of Convective Activity Using Stability Indices as Inferred from Radiosonde and MODIS Data
AUTHORS:
P. R. Jayakrishnan, C. A. Babu
KEYWORDS:
Atmospheric Thermodynamics; Stability Indices; Convection
JOURNAL NAME:
Atmospheric and Climate Sciences,
Vol.4 No.1,
January
15,
2014
ABSTRACT: The combined use of both radiosonde data and three-dimensional
satellite derived data over ocean and land is useful for a better understanding
of atmospheric thermodynamics. Here, an attempt is made to study the thermodynamic
structure of convective atmosphere during pre-monsoon season over southwest
peninsular India utilizing satellite derived data and radiosonde data. The stability
indices were computed for the selected stations over southwest peninsular India
viz: Thiruvananthapuram and Cochin, using the radiosonde data for five premonsoon
seasons. The stability indices studied for the region are Showalter Index (SI),
K Index (KI), Lifted Index (LI), Total Totals Index (TTI), Humidity Index (HI),
Deep Convective Index (DCI) and thermodynamic parameters such as Convective
Available Potential Energy (CAPE) and Convective Inhibition Energy (CINE). The
traditional Showalter Index has been modified to incorporate the thermodynamics
over tropical region. MODIS data over South Peninsular India are also
used for the study. When there is a convective system over south peninsular
India, the value of LI over the region is less than ?4. On the other hand, the
region where LI is more than 2 is comparatively stable without any convection.
Similarly, when KI values are in the range 35 to 40, there is a possibility for
convection. The threshold value for TTI is found to be between 50 and 55.
Further, we found that prior to convection, dry bulb temperature at 1000, 850,
700 and 500 hPa is minimum and the dew point temperature is a maximum, which
leads to increase in relative humidity. The total column water vapor is maximum
in the convective region and minimum in the stable region. The threshold values
for the different stability indices are found to agree with that reported in
literature.