Observations of daytime surface energy balance in cloudy tropical conditions at Ile-Ife, Nigeria

Daytime energy balance at the surface in cloudy tropical conditions for Ile-Ife; Nigeria (7°33'N, 4°34'E) is investigated based on a series of micrometeorological measurements performed in October/November of 1998. For the humid environment that it is (mixing ratio, 17 -25 g / kg), magnitudes of the latent heat flux were much larger than the values for the sensible heat. Of the morning hours the average value for the Bowen ratio obtained was 0.36, while for the afternoons it was 0.74. As the soil surface became dried up in the afternoons, magnitudes of both sensible heat and ground heat fluxes were found to be comparable. Fluctuations in the magnitudes of the terms of the surface energy balance correlated well to the cloud amount, degree of soil wetness, air temperature and humidity. But of all these factors, the variation in the amount of cloudiness appeared most dominant.

Development of 1961-1990 monthly surface climatology of India and patterns of differences of some meteorological parameters with respect to the 1951-1980 climatology

Climate normals are used to describe the average climatic conditions of a particular place and are computed by National Meteorological Services of all countries. The World Meteorological Organization (WMO) recommends that all countries prepare climate normals for the 30-year periods ending in 1930, 1960, 1990 and so on, for which the WMO World Climate Normals are published. Recently, Climatological Normals for the period 1961-1990 have been prepared by India Meteorological Department (IMD) which will change the baseline of comparison from 1951-1980. In this paper, preparation of the 30-year Climatological Normals of India for the period 1961 to 1990 and spatial patterns of differences of annual means of temperatures, relative humidity, clouds, rainfall and wind speed from the previous normals (1951-1980) are documented.The changes from earlier climatological normals indicate increase in annual means of maximum temperature, relative humidity and decrease in annual means of minimum temperature, cloud amount, rainfall, rainy days and wind speed over large parts of the country during 1961-1990. The spatial patterns of changes in dry bulb temperatures and relative humidity are complementary over most parts of the country. Compared with 1951-1980 climatology, there are large scale decreases in annual mean rainfall, rainy days and wind speed over most parts of the country during 1961-1990. The decrease in wind speed may be partly due to changes in exposure conditions of observatories due to urbanization.

Forecasting of minimum temperature over Gangtok

A study has been conducted to assess day-to-day changes, departure and persistence of minimum temperature and the frequency of cold wave and severe cold wave over Gangtok for five winter months i.e., November-March for the years 1969 to 1992. Regression models have also been formulated to forecast minimum temperature with the knowledge of dew point, cloud amount, maximum temperature and minimum temperature recorded on previous day. In case of changes, ‘little change’ and ‘no change’ constitute about four-fifth of total changes. The cases of nearly normal were found maximum when departure of minimum temperature from normal was considered. Frequency of cold wave and severe cold wave has been recorded more in January and February respectively. It has been observed that there is a gradual fall in the percentage frequency with the increase in the magnitude of variation. Regression model gives good results from November to February.

On some characteristics of the field intensity of atmospherics ant at Calcutta due to local active monsoon clouds

The paper examines some characteristics of the field intensity level of atmospherics at three harmonically related frequencies due to local active monsoon clouds. Seasonal variations of the ratio of afternoon maximum to morning minimum as well as that of the afternoon minimum to morning minimum of atmospherics and the local rainfall have been critically analysed. The differences of the two ratios exhibit a pronounced seasonal variation, having minimum values during the monsoon months and also the significance ratio at such times decreases with the increase of rainfall. which. in turn. is related to local sferics. The results further indicate how the overhead cloud amount in okta contributes significantly over the intensity level of different frequencies and width of atmospherics.

Estimation of relative humidity profiles From INSAT cloud data

Accurate humidity profiles are needed for obtaining useful rainfall forecasts from numerical weather prediction models. In this context objective estimation of moisture profiles over ocean areas using satellite cloud data becomes important. For this purpose the fractional cloudiness data available from INSAT has been classified into different cloud categories depending on the total cloud amount and the levels at which the clouds have been present. Actual relative humidity profiles have been obtained using TEMP data of Port Blair (11 .6°N 92.7°E) and Minicoy (8,3°N, 72,9°E), Most frequently occurring relative humidity profile has been selected as being representative of humidity distribution in the vertical for a given cloud category. The preliminary results reported here show that these bogus relative humidity profiles could provide useful Information on moisture distribution in the vertical over the Indian Ocean.

The role of anthropogenic aerosols in the anomalous cooling from 1960 to 1990 in the CMIP6 Earth system models

The Earth system models (ESMs) that participated in the sixth Coupled Model Intercomparison Project (CMIP6) tend to simulate excessive cooling in surface air temperature (TAS) between 1960 and 1990. The anomalous cooling is pronounced over the Northern Hemisphere (NH) midlatitudes, coinciding with the rapid growth of anthropogenic sulfur dioxide (SO2) emissions, the primary precursor of atmospheric sulfate aerosols. Structural uncertainties between ESMs have a larger impact on the anomalous cooling than internal variability. Historical simulations with and without anthropogenic aerosol emissions indicate that the anomalous cooling in the ESMs is attributed to the higher aerosol burden in these models. The aerosol forcing sensitivity, estimated as the outgoing shortwave radiation (OSR) response to aerosol concentration changes, cannot well explain the diversity of pothole cooling (PHC) biases in the ESMs. The relative contributions to aerosol forcing sensitivity from aerosol–radiation interactions (ARIs) and aerosol–cloud interactions (ACIs) can be estimated from CMIP6 simulations. We show that even when the aerosol forcing sensitivity is similar between ESMs, the relative contributions of ARI and ACI may be substantially different. The ACI accounts for between 64 % and 87 % of the aerosol forcing sensitivity in the models and is the main source of the aerosol forcing sensitivity differences between the ESMs. The ACI can be further decomposed into a cloud-amount term (which depends linearly on cloud fraction) and a cloud-albedo term (which is independent of cloud fraction, to the first order), with the cloud-amount term accounting for most of the inter-model differences.

Normalized anomaly patterns of meteorological elements: A case study of Northeast monsoon 2002 and 2004

ekSle foKkfud vk¡dM+ksa dks lkekU;h—r folaxfr;ksa ds laca/k esa crkuk izk;% lgk;d jgrk gS D;ksafd blls lkekU; cuke vlkekU; ekuksa dks igpkuuk ljy gks tkrk gSA blds vykok blls LFkku ds izHkko rFkk vk¡dM+ksa ds izlkj dk izHkko nwj gksrk gS vkSj nks fHkUu LFkkuksa esa izs{k.kksa dh rqyuk lqfo/kktud gks tkrh gSA bl izdkj lkekU;h—r folaxfr ¼,u- ,-½ iSVuZ vFkkZr fu/kkZfjr le; esa folaxfr;ksa dk LFkkfud forj.k izfrdwy ekSle dh ?kVukvksa esa iwokZuqekudrkZvksa ds fy, ,d l’kDr midj.k cu tkrk gSA bl 'kks/k i= esa mRrjiwohZ ekWulwu 2002 dh varj&ekSleh fof’k"V iz—fr ij fopkj djrs gq, ekSle dh izfrdwy ?kVukvksa dk fo’ys"k.k djus ds fy, ,u- ,- iSVuZ ds mi;ksx ij dk;Z fd;k x;k gSA mRrj iwohZ ekWulwu 2002 ds nkSjku lw[ks tSlh fLFkfr;ksa ds ckjs esa foLrkj ls ppkZ dh xbZ gS vkSj muds dkj.kksa dh tk¡p dh xbZ gSA ;g Hkh ns[kk x;k gS fd mRrj iwohZ ekWulwu 2002 ds varj ekSleh iz—fr iSVuZ esa izsf{kr lw[ks tSls fLFkfr dk ,d dkj.k 200 ,p- ih- ,- Åijh ry fjt dk gksuk vFkok ldkjkRed HkwfoHko Å¡pkbZ folaxfr] uoEcj esa lkbcsfj;u gkbZ esa udkjkRed ek/; leqnz Lrj nkc folaxfr] 200 ,p- ih- ,- iou folaxfr dh rhozrk gks ldrk gSA fuEu es?k ek=k] 'kq"d cYc rkieku vkSj lkis{k vknzZrk ls mRrj iwohZ ekWulwu 2002 esa lw[ks tSlh fLFkfr;ksa dk irk pyk tcfd vkSlr iou xfr ds ,u- ,- ls caxky dh [kkM+h esa pØokrksa ds {kh.k gksus vkSj izk;}hih; Hkkjr rd ugha igq¡pus ds ckjs esa irk pykA mRrj iwohZ ekWulwu 2004 ds fy, fuEu es?k ek=k] lkis{k vknzZrk] 'kq"d cYc rkieku rFkk vkSlr iou xfr ds ,u- ,- iSVuZ ls mRrj iwohZ ekWulwu 2002 ds ekeys esa bu ekSle foKkfud izkpyksa ds fy, ,u- ,- iSVuZ esa lw[ks tSls fLFkfr;ksa ds izs{k.kksa dh iqf"V gqbZA It is often helpful to express the meteorological data in terms of normalized anomalies as they make it easier to discern normal versus unusual values. Also it removes influence of location and spread from data and facilitates the comparison of observations at two different locations. Thus, Normalized Anomaly (NA) patterns i.e., spatial distribution of anomalies at specified time make a powerful tool in hand of forecasters to analyze extreme events. The present study explores the utilization of NA patterns for the purpose of analyzing extreme events by focusing on the inter-seasonal peculiar behavior of Northeast monsoon 2002. A detailed discussion is given and reasons are explored for droughts like situations during Northeast monsoon 2002. It was also noticed that the persistence of 200 hPa upper level ridge or positive geopotential height anomaly, negative mean sea level pressure anomaly over Siberian High during November, strength of 200 hPa wind anomaly can be one of the reasons for drought-like situation observed in the inter-seasonal behavior pattern of Northeast monsoon 2002. NA patterns of low cloud amount, dry bulb temperature and relative humidity captured drought-like situations during Northeast monsoon 2002 while NA of average wind speed captured the scenario of dissipating cyclones in the Bay of Bengal itself and not reaching to Peninsular India. The NA patterns of low cloud amount, relative humidity, dry bulb temperature and average wind speed for Northeast Monsoon 2004 confirm the observations of drought like situations seen in NA patterns for these meteorological parameters in case of Northeast monsoon 2002.

Sunshine duration climatology and trends in association with other climatic factors over India for 1970-2006

Changes in sunshine duration in association with total cloud amount, rainy days and good visibility days over India were examined for 1970-2006. Climatologically, annual total sunshine duration over west Rajasthan and adjoining Gujarat is more than 3100 hours which is ideal for harnessing solar energy over these regions. The trend analysis indicates significant decrease in sunshine duration over the country for all months (except June) and the maximum decrease has taken place in January (-0.44 hour/decade) followed by December (-0.39 hour/decade). Seasonally, decline in sunshine hours is highest in winter and post monsoon (4% per decade) and lowest in monsoon (3% per decade). Decadal variations indicate maximum decrease in sunshine over the Indo-Gangetic plains and south peninsula during 1990-1999. Spatially, the decreasing trends in sunshine hours are highest in Indo-Gangetic plains and south peninsula while regions over Rajasthan and Gujarat have lowest decrease. Out of 40 stations under study, the maximum decrease in sunshine has occurred at New Delhi (winter at 13% per decade and post monsoon at 10% per decade) and Varanasi (summer and monsoon at 7% per decade). Correlation analysis of sunshine duration with total cloud amount, rainy days and good visibility days indicates regional and seasonal variations in factors explaining the long term trends in sunshine duration over the country.

Recent trends in meteorological parameters over Jammu and Kashmir

Annual trends of meteorological parameters temperature, rainfall, relative humidity and clouds for ten stations in Jammu and Kashmir during the period 1976-2007 were studied. Trend analysis shows that temperatures are increasing over the state with significant increase in maximum temperature in the Kashmir region (+0.04 to + 0.05° C/year) and minimum temperature in the Jammu region (+0.03 to + 0.08° C/year). The diurnal temperature range (DTR) is increasing over Kashmir region due to higher increasing trends in the maximum temperature while the strong increasing trends in the minimum temperature are contributing more towards the decrease in DTR over the Jammu region. Annual rainfall and rainy days trends are decreasing in both the regions of the state except at Jammu where rainfall trend is significantly increasing (+12.05 mm/year). Day-time relative humidity trends are mixed while total cloud amount trends are decreasing over Kashmir region and increasing over Jammu region. The effects of urbanization in the last two decades are more pronounced in Jammu region and this is strongly expressed in minimum temperature over the region. The warming trends observed over Jammu and Kashmir state during the period of study need further investigation in relation to variability of atmospheric circulation over North India.