Abstracts for the 5th International GAME Conf.

3-5 October 2001

Aichi Trade Center

Nagoya Japan

The Effect of El Nino and Southern Oscillation (ENSO) on Atmospheric Water Resources over Northeast Part of Thailand

Mr. Prasert Aungsuratana (1)

The atmospheric water resources (AWR) are the blanket of the humid air and its rainfall potential surrounding the earth surface. The investigation on the effect of ENSO on AWR are carried on by using twenty years data of daily synoptic situation, daily upper-air observation over northeast part (NE) (Meteorological Department, 2000) and compare these data to the multivariation ENSO index (MEI) which introduced by Wolter and Timlin (1993). The result reveal that apparently, atmospheric flow over NE are classified into 5 periodicals (Silverman et al, 1986). These are: 1) Summer Inter monsoonal (SIM) March and April; 2) On-set Southwest Monsoon (OSM), May and June; 3) Southwest Monsoon (SM), July, August and September; 4) Winter Inter-monsoonal (WIM), October; and 5) Northeast Monsoon (NEM), November to March. In SIM, dominant affecting on AWR over NE are the active high pressure (AH) extends its ridge to the heat low cell, as well as the confluence of southeasterly and southerly or southwesterly wind (CON). Both situation induce the unstable air producing area of convective precipitation. In warm ENSO periods (positive value of MEI), there are the less frequency and short duration of AH and CON than the negative MEI. For example, in April 1998 (dry) compare to April 1999 (wet), the dry month had less frequency and shorter duration of AH and CON than the wet month. In OSM, AWR is dominant affected by the occurrence of the intertropical convergence zone (AITCZ) lies across upper Thailand to active low pressure or tropical storms (TS) over south China sea or Andaman sea. These conditions, flow from Indian ocean bring moist convectively unstable air to over inland. TS usually occurs in Andaman sea and move northward to Myanmar. Low intensity and short duration of ITCZ are affected by the warm ENSO, for example, in May 1992 and May 1997. Those conditions also affect to the day on-set of southwest monsoon (SW) for example, in May 1997(dry), SW was on-set after the normal condition (May,16) around 15 days. On the other hand, in cold ENSO, for example, in May, 1999, SM was On-set on April 16, a month before the normal condition. In SM, it has similar to the OSM condition. In WIM, AWR is dominant affected by the movement of ITCZ associate with AH. Warm ENSO is influence on rapidly moving downward of ITCZ and AH. In NM it is the dry season of NE, little rainfall come from AH and CON. ENSO condition is not clearly affect on AWR. About upper-air observation, it indicates that weather situation relates to the humidity and stability indicies (SI) of atmospheric profile. The warm ENSO are relate to low humidity and the stable condition. For example, the height of 700 mb and 500 mb levels of warm ENSO days (August, 1993) are higher than those on cold ENSO days (August, 1996). And also the precipitable water (PW) of the days in August, 1996 are more than those in August, 1993. In addition, the analysis of the relationship between the synoptic weather situation and MEI indicated the significance.

Submittal Information

Name : Date :
    Mr. Prasert Aungsuratana
    29-May-01-12:28:32
Organization : Theme :
    Bureau of the Royal Rainmaking and Agricultural Aviation (BRRAA), Ministry of Agricultural and Cooperatives
    Theme 1
Address : Presentation :
    Bureau of the Royal Rainmaking and Agricultural Aviation (BRRAA), In Kaset sart University Campus, Bangkok 10900
    Poster or oral
Country : Abstract ID :
    Thailand
    T1MPA29May01122832
Phone : Fax :
    +66 2 9405960 ext. 126, 127, 5613028
    +66 2 5613028
E-mail :
    warawut@mozart.inet.co.th