Some statistical characteristics of occurrence of fog over Patna airport

bl 'kks/k i= esa o"kZ 2000 ls 2010 rd 10 o"kksZa ds uoacj ls Qjojh ekg  dh vof/k ds vk¡dMksa dk mi;ksx djrs gq, iVuk gokbZ vMMs ij Nkus okys dqgjs dh lkaf[;dh; fo’ks"krkvksa tSls & dksgjk Nkus dh ckjEckjrk] Nkus dk le;] vof/k] l?kurk rFkk folfjr gksus ds le; dk  v/;;u fd;k x;k gSA bl v/;;u ls izkIr gq, ifj.kke ls irk pyk gS fd foxr 10 o"kksZa ds nkSjku iVuk gokbZ vMMs ij pkjksa gh eghuksa esa dqgjs dh ckjEckjrk  esa o"kZ 1961&90 rFkk 1951&80 ds tyok;fodh esa miyC/k flukWfIVd rFkk rRdkfyd ekSkle izs{k.kksa dh rqyuk esa fo’ks"k :i ls o`f) gqbZ gSA iVuk gokbZ vMMs ij dqgjk Nkus dk lcls vuqdwy eghuk fnlEcj vkSj mlds ckn tuojh dk ekuk x;k gsA fnlacj vkSj tuojh ds eghuksa esa 5 ?kaVsa ls vf/kd vof/k rd  dqgjk Nkus dh vko`fRr  dh izfr’kr~rk vf/kdre jgh gS tcfd uoacj ,oa Qjojh ds eghuksa esa 2 ?kaVs ls de vof/k dh vko`fRr lcls vf/kd jgh gSA dqgjk dk cuuk vDlj 0000&0200 ;w-Vh-lh- ds nkSjku vkSj bldk {k; gksuk  0200&0500 ;w- Vh- lh- ds nkSjku ns[kk x;k gSA cgqr ?kus dqgjs dh vf/kdre vko`fRr & izfr’krrk uoacj ekg esa ns[kh xbZ gSA fnlacj vkSj tuojh ds eghuksa dh vf/kdrj fLFkfr;ksa esa 1200 ;w-Vh-ij vxyh jkr@lqcg ds le; iMs+ dksgjs ds jsfM;ksa lkSans ds vk¡dMksa ds vk/kkj ij rS;kj fd, x, dqgjk LFkkf;Ro lwpdkad ¼,Q-,l-vkbZ-½ 40 ls de ik;k x;k gSA  In this paper some statistical characteristics of fog, such as frequencies of occurrence, time of onset, duration, intensity and time of dispersal  over Patna airport are studied  making use of 10 years data for the period November-February, 2000-2010.  The result shows that during the last ten years frequency of fog over Patna airport has increased significantly in all the four months as compared to the climatology based on available synoptic and current weather observations during 1961-90 and 1951-80. The most favourable month for occurrence of fog over Patna airport has been identified as December followed by January. Percentage frequency is highest for duration of fog for more than 5 hours in the months of December and January whereas in the months of November and February frequency is highest for duration less than 2 hours. The formation of fog mostly observed during 0000-0200 UTC and dissipation during 0200-0500 UTC. Percentage frequency of very thick fog was found to be highest in the month of November. In the   months of December and January in most of the cases Fog Stability Index (FSI) based on 1200 UTC radiosonde data leading to occurrence of fog during following night/morning has been found to be less than 40.