Based?on?the data of conventional?meteorological?observations,?microwave?radiometer? retrieval?data,?Rongcheng?L-band?radiosonde?observations, ECMWF (European Centre for Medium- Range Weather Forecasts) Reanalysis v5 (ERA5) and NOAA ( National Oceanic and Atmospheric Administration), three?typical?non-precipitation?sea?fog?cases?occurring?on?the?northern?Yellow?Sea?from? May?to?July?2024?have been?analyzed.?By?validating?the?correlation?between?temperature?and?humidity? profiles?derived?from?microwave?radiometers?and?L-band?radiosondes?(correlation?coefficients?>0.5? below?2?km),?a?foundation?for?data?reliability?is?established.?This?study?focuses?on?differences?in?the? thermal-humidity?structures?and?formation?mechanisms?of?sea?fog?under?varying?synoptic?systems.?Key? findings?include: (1)?Hybrid?sea?fog?transitioning?from?high-pressure?rear?to?low-pressure?front?persists?for? over?2?days,?exhibiting?pronounced?diurnal?variations.?The?day-night?air-sea?temperature?difference?exceeds?12 °C.?During?daytime,?the?temperature?inversion?layer?weakens?in?both?intensity?and?thickness,?accompanied?by? reduced?relative?humidity,?while?nighttime?conditions?reverse.?Liquid?water?content?concentrates?at?0.1-0.2?km? altitude,?peaking??at?0.57?g·m-3 before?the?densest?fog?formation.?The formation process is dominated by? humidification?and?cooling?effects.?(2) Weak?cold-front?fog?event?occurs?at?night?and?early?morning, lasting for several hours. Under the influence of the cold front, the temperature drops rapidly, and water vapor condenses to form a front fog. The highest in the high humidity area is 300 m, which is shallow compared with the advection cooling fog?, with?air-sea?temperature?differences?dropping?to?-0.1°C. The maximum liquid water content is 0.9 g·m-3, which occurs at the lowest temperature and before thicker fog appears. The formation process is dominated by cooling. (3) Summer-prevailing?advection cooling? fog?is?closely?linked?to?the?stable?subtropical?high.?Compared?to?the?first two cases,?this?fog?persists?longer?days,?with?weaker?vertical?temperature?gradients?and?smaller?diurnal?temperature?fluctuations.?The?maximum? temperature?difference?within?the?inversion?layer?is?only?3.81°C,?yet?it?exhibits?abundant?and?prolonged?liquid? water?content,?exceeding?1.0?g·m-3,?with?significant?humidification?effects.