Extent of diurnal cycle of rainfall and its intra seasonal variation over coastal Tamil Nadu during north east monsoon season

The diurnal variation of north east monsoon rainfall of coastal Tamil Nadu represented by four coastal stations Chennai Nungambakkam (Nbk), Chennai Meenambakkam (Mbk), Nagapattinam (Npt) and Pamban (Pbn) was studied in detail based on hourly rainfall data of rainy days only, for the period 1 Oct-31 Dec for the 47/48 year period 1969-2016/2017. Mean Octet rainfall and its anomaly were computed for the 8 octets 00-03,…., 21-24 hrs of the day and the anomaly was tested for statistical significance. Various analysis for the individual months of Oct, Nov, Dec and the entire period Oct-Dec were separately conducted. The basic technique of evolutionary histogram analysis supplemented by harmonic analysis of octet mean rainfall anomaly was used to detect the diurnal cycle signal. Two indices named as diurnal variation of rainfall index and coefficient of mean absolute octet rainfall anomaly representing the intensity of diurnal variation in dimensionless numbers were defined, computed and interpreted. The analysis based on the above techniques revealed that the diurnal signal which shows an early morning maximum and late afternoon minimum of octet rainfall is well defined in Oct, decreases in Nov and further decreases in Dec for all the 4 stations. Though the diurnal variation manifests a well defined pattern in Dec the signal is not statistically significant in most cases. For Nbk and Mbk there is a weak secondary peak of octet rainfall anomaly occurring in the forenoon and afternoon respectively in Oct and Dec suggesting the presence of semi-diurnal variation of rainfall. Stationwise, the diurnal signal is most well defined for each month/season in Pbn followed by Npt, Nbk and then Mbk. The physical causes behind the diurnal signal and its decrease as the north east monsoon season advances from Oct to Dec have been deliberated. The well known feature of nocturnal maximum of oceanic convection influencing a coastal station with maritime climate and the higher saturation at the lower levels of the upper atmosphere in the early morning hours have been advanced as some of the causes. For the much more complex feature of decrease of diurnal signal with the advancement of the season, the decrease of minimum surface temperature over coastal Tamil Nadu from Oct to Dec causing an early morning conceptual land breeze has been shown as one of the plausible causes based on analysis of temperature and wind. Scope for further work based on data from automatic weather stations, weather satellites and Doppler Weather Radars has been discussed.

Climatological characteristics of sea breeze parameters at Chennai

Several sea breeze parameters such as time of onset, withdrawal, duration, depth, variation with height, direction etc. have been derived and studied for Chennai city and Chennai AP observatories in this study, which has been based on a large data base for the period March-October,1969-83. The monthly and sub monthly values of several sea breeze parameters have been derived. By invoking the concept of superposed epoch analysis the important role played by sea breeze in modulating diurnal variation of surface temperature and relative humidity has been established. The sea breeze at Chennai has been shown to be shallow with a depth of under 1 km. Modal directions of sea breeze and its normal speed have been derived.

Biometeorological Conditions during the August 2015 Mega-Heat Wave and the Summer 2010 Mega-Heat Wave in Ukraine

The human-biometeorological conditions in Ukraine during two mega-heat waves were analyzed. The evaluation is based on physiologically equivalent temperature (PET). The calculation of PET is performed utilizing the RayMan model. The results revealed these two mega-heat waves produced strenuous human-biometeorological conditions on the territory of Ukraine. During the summer 2010 mega-heat wave, strong and extreme heat stress prevailed at about midday at the stations where this atmospheric phenomenon was observed. The mega-heat wave of August 2015 was characterized by a lower heat load. The diurnal variation of PET values during the researched mega-HW was similar to that of the diurnal variation of air temperature with minimum values in the early morning and maximum values in the afternoon. On the territory where mega-heat waves were observed, the number of days during which heat stress occurred for 9 h amounted to 97.6% for the period from 31 July to 12 August 2010 and 77.1% for the mega-heat wave of August 2015.

Face Validity of Observed Meal Patterns Reported with 7-Day Diet Diaries in a Large Population-Based Cohort Using Diurnal Variation in Concentration Biomarkers of Dietary Intake

In a cross-sectional analysis of a population-based cohort (United Kingdom, N = 21,318, 1993–1998), we studied how associations between meal patterns and non-fasting triglyceride and glucose concentrations were influenced by the hour of day at which the blood sample was collected to ascertain face validity of reported meal patterns, as well as the influence of reporting bias (assessed using formula of energy expenditure) on this association. Meal size (i.e., reported energy content), mealtime and meal frequency were reported using pre-structured 7-day diet diaries. In ANCOVA, sex-specific means of biomarker concentrations were calculated by hour of blood sample collection for quartiles of reported energy intake at breakfast, lunch and dinner (meal size). Significant interactions were observed between breakfast size, sampling time and triglyceride concentrations and between lunch size, sampling time and triglyceride, as well as glucose concentrations. Those skipping breakfast had the lowest triglyceride concentrations in the morning and those skipping lunch had the lowest triglyceride and glucose concentrations in the afternoon, especially among acceptable energy reporters. Eating and drinking occasion frequency was weakly associated with glucose concentrations in women and positively associated with triglyceride concentrations in both sexes; stronger associations were observed for larger vs. smaller meals and among acceptable energy reporters. Associations between meal patterns and concentration biomarkers can be observed when accounting for diurnal variation and underreporting. These findings support the use of 7-day diet diaries for studying associations between meal patterns and health.

Diurnal variation of cloudiness during southwest monsoon season using I NSAT-IB radiance data

An attempt has been made to study the diurnal variation of convective clouds. For this study 3 hourly full resolution infrared data of INSAT-IB have been used for the monsoon season (Jun-Sep) of 1987-89. The area of study extends from 35°N to 25°S and 40oE to l00oE, which is subdivided into small areas of 2.5x 2.5 Lat./Long. Mean temperature and the fractional area covered by clouds colder than a given threshold temperature over each sub area are the parameters used for this study. Two threshold temperatures. namely 265°K & 235oK are chosen to represent convective clouds and deep convective clouds respectively. Using the three hourly observations, times of maximum and minimum convective activity are also obtained. Maximum convective activity is observed over head Bay of Bengal at about noon and this maximum migrates westward onto land till midnight and swings back to oceanic area by morning. This eastwest oscillation is less over equatorial regions (open ocean).

Analysis of solar radiation measurements at EI-Kharga (250 N, 300E), Egypt

Daily global solar. radiation data of EI-Kharga for five year (1984-88) have been processed, analysed and classified into eight radiation levels spaced at an interval of 4.19 MJ m-2 day-l. Mean annual monthly and daily total the diurnal variation, and the frequency distribution of daily totals of global solar radiation are computed and discussed. A correlation between the hourly values of the clearness and diffuse indices were obtained and the recommended correlation ,equations were also given. The, results presented in this analysis are encouraging since they Indicate that periods of several days of low radiation of less than 8.38 MJm , day are rare. This In turn means that the weather sequence variations are not expected, to be of great Importance when considering the storage problems Involved In solar process design.