ASSESSMENT OF OUTDOOR THERMAL HUMAN COMFORT OVER BEIRUT CITY, LEBANON

. ABSTRACT This study applied Thom's Discomfort Index (DI), Kibler Discomfort Index (THI 1 ) (Temperature-Humidity Index) and National Oceanic and Atmospheric Administration (NOAA) Discomfort Index (THI 2 ) to assess the trend of thermal discomfort in Beirut City during )1999-2021(. Temperature and relative humidity data for twenty-two years (1999-2021) from Beirut-Rafic Hariri International Airport (BRHIA) station were analyzed to determine the discomfort period. Seasonal variations in thermal conditions were found, with increased thermal stress levels occurring mainly during Summer, while Spring and Winter showed improved thermal comfort conditions with respect to Summer. December, January, and February were comparatively comfortable (DI < 21). Under 50% of the population experienced discomfort (21 < DI < 24) during March and November. From May to September, discomfort values varied between 25-27, which indicates that over 50% of population in Beirut suffered from discomfort during these months. Percentage frequencies of the monthly (DI) values from January to December in Beirut from the years 1999 to 2021 were also reported. Monthly variations of (THI 1 ) and (THI 2 ) showed no extreme discomfort conditions in Beirut. Data on air temperatures and relative humidity in Beirut were