Category: Meteorology


Ref FAA-H-8083-25C version 2023 5-24, 7-12, 11-8,12-17 Ceiling related to metrology? Ceiling is the lowest layer of clouds reported as being broken (5/8) or overcast (8/8) OR the vertical visibility into an obscuration like fog or haze     Ceiling related aircraft performance? absolute ceiling : the altitude at which the aircraft has no excess Read More

When the air is stable?

Ref: 到底咩情況下parcel of air 叫stable? To answer this question, we need understand few concept: 咩係Lapse rate 咩係環境上面既Lapse rate 咩係pacel of air 既Lapse rate   Lapse Rate is the rate at which temperature changes with height in the Atmosphere. In my language, how many degree Celsius drop when vertical distance increase for a fixed number.   Read More

What’s Monsoon Wind ; Why Monsoon blow from north east in winter and southwest in summer?

Ref:   所謂季候風就係會隨著季節改變既風, 但光是研究呢個季候風既風向都搞左我粒幾鐘, 因為背後講緊既CONCEPT 有好幾個: 咩叫High pressure system, 咩叫Low pressure system 咩係風 咩叫Coriolis effect (科里奧利力/科科氏力) 咩叫Geostrophic Wind (地轉風)   想簡單D咁理解就要背少少野 (明白少少基本CONCEPT) High, Low pressure system 是相對 (relative) : compare one air mass with another one 仲要記得通常凍就係有高壓區, 熱就係有低壓區~ 風就是due to two air mass has pressure difference and so the pressure gradient as Read More

What’s CAVOK , What’s NCD, NSC

Reference source: CAVOK The visibility, RVR, weather and cloud groups are replaced by CAVOK (Cloud And Visibility OK) when the following conditions exist simultaneously: If there is no cloud below 5000 ft or below the highest minimum sector altitude (whichever is greater) and there is no towering cumulus or cumulonimbus, ‘NSC’ is reported. Note: Read More