Evaluation of the Vertical Temperature Profile over Shiraz Station by Using Radiosonde Data: Connection between Temperature and Precipitation

Analyzing temperature profile of the Earth''s atmosphere is an essential work for understanding the dynamic¡ radiative and chemical processes occur within the atmosphere and its boundary layers. Such analysis is also critical for the detection and modeling of climate change. Several studies is made on different temporal and spatial scales of the vertical structure of the atmosphere. Expanding knowledge and technology of remote sensing is also helpful to identify the vertical profile of the atmosphere. For better understanding the characteristics of vertical temperature profile in southern parts of Iran¡ daily records of radiosonde data at Shiraz station (Latitude 29.6N and Longitude 52.5E) were collected for the period 2005-2010. The dataset consisted of pressure¡ temperature and relative humidity data gathered from surface up to 30 Km above sea level at 0:0 Greenwich Mean Time GMT (3:30 am local time). Daily data were firstly transformed to monthly and seasonal time-series using arithmetic averaging procedure. There was no significant changes in pattern of vertical profiles of temperature fluctuations in the years studied. The study has found a temperature inversion layer¡ mostly having vertical length from 100 to 300 meters above surface level for all months of the year. The layer length was shorter when the relative humidity was greater. Temperature gradient changes to negative at the height of 1760-1580 meters above sea level. A lapse rate with the measure of 4Co/ Km during cold months and 6Co/Km during warm months was detected between the top of inversion layer and tropopause level. Maximum and minimum heights of tropopause were occurred during March and December 2009 (16494 and 19006 meters)¡ respectively. Result showed that according to global warming¡ variation in tropopause elevation trend in Shiraz station not only increase but also decrease. Tropopouse height changes from month to month and from year to year and we could not find any rule for it. Maybe these conflicts are because of short period of investigation. Tropopouse minimum temperature occurs in Jun and July and it is about -74 to -77.5 degrees Celsius .Maximum temperature occurs in December and January and it is closed to -68 degrees Celsius. Average annual value of tropopause temperature was estimated as (-71.6 Co). The coldest and warmest tropopause data were associated to the warm and cold months of the year¡ respectively. In seasonal scale¡ while the highest tropopause height occurred during winter (18138 meters)¡ the lowest elevation was associated to autumn (17158 meters). According to global regularity tropopause height increase in the warm months¡ but in this study it was proven otherwise because the maximum height of tropopause see in winter and it is due to the characteristics of a tropical latitude30 °and being in Subtropical Jet Stream path. Some discrepancies were found between our results and the findings of Australian investigator who analyzed Australian data (Khandu et al.¡ 2011). Discussion was made to justify these differences..Temperature gradient was found positive over the lower parts of stratosphere (up to 30 Km level). The highest or lowest increasing gradient was 1 or 2 oC per Kilometer¡ which happened during cold or warm months of the year¡ respectively.