Summer Arctic sea fog

Synchronous or quasi-synchronous sea-land-air observations were conducted using advanced sea ice, atmospheric and marine instruments during China's First Arctic Expedition. Expedition.Based on the Precious data from the expedition, it was found that in the Arctic Ocean, most part of which is covered with ice or is mixed with ice, various kinds of sea fog formed such as advection fog, radiation fog and vapor fog. Each kind he its own characteristic and mechanics of creation. In the southern part of the Arctic Ocean, due to the sufficient warm and wet flow there, it is favorable for advection fog to form, which is dense and lasts a long time. On ice cap or vast floating ice, due to the strong radiation cooling effect, stable radiating fog is likely to form. In floating ice area there forms vapor fog with the appearance of masses of vapor from a boiling pot, which is different from short-lasting land fog. The study indicates that the reason why there are many kinds of sea fog form in the Arctic Ocean is because of the complicated cushion and the consequent sea-air interaction caused by the sea ice distribution and its unique physical characteristics. Sea fog is the atmospheric phenomenon of sea-air heat exchange. Especially, due to the high albedo of ice and snow surface, it is diffcult to absorb great amount of solar radiation during the polar days. Besides, ice is a poor conductor of heat; it blocks the sea-air heat exchange. The sea-air exchange is active in floating ice area where the ice is broken. The sea sends heat to the atmosphere in form of latent heat; vapor fog is a way of sea-air heat exchange influencing the climate and an indicator of the extent of the exchange. The study also indicates that the sea also transports heat to the atmosophere in form of sensible heat when vapor fog occurs.

Numerical Simulations of an Advection Fog Event over Shanghai Pudong International Airport with the WRF Model

A series of numerical simulations is conducted to understand the formation, evolution, and dissipation of an advec- tion fog event over Shanghai Pudong International Airport （ZSPD） with the Weather Research and Forecasting （WRF） model. Using the current operational settings at the Meteorological Center of East China Air Traffic Manage- ment Bureau, the WRF model successfully predicts the fog event at ZSPD. Additional numerical experiments are per- formed to examine the physical processes associated with the fog event. The results indicate that prediction of this particular fog event is sensitive to microphysical schemes for the time of fog dissipation but not for the time of fog onset. The simulated timing of the arrival and dissipation of the fog, as well as the cloud distribution, is substantially sensitive to the planetary boundary layer and radiation （both longwave and shortwave） processes. Moreover, varying forecast lead times also produces different simulation results for the fog event regarding its onset and duration, sug- gesting a trade-off between more accurate initial conditions and a proper forecast lead time that allows model physi- cal processes to spin up adequately during the fog simulation. The overall outcomes from this study imply that the complexity of physical processes and their interactions within the WRF model during fog evolution and dissipation is a key area of future research.

NUMERICAL PREDICTION EXPERIMENT OF AN ADVECTION FOG IN NANLING MOUNTAIN AREA

Now more comprehensive cloud microphysical processes have been included in advanced three- dimensional mesoscale meteorological model such as PSU/NCAR MM5 model,so the model can be used in the prediction of fog.In this paper,MM5 was utilized to simulate an advection fog occurring in Nanling Mountain area.The simulated results were compared with the facts obtained by detailed observation experiment.The results showed that the simulation was successful in the following aspects:(1)the formation and development of the fog;(2)the temporal variation of the maximum liquid water content;(3)the diffusion of the cold air,especially the temporal variation of the ground temperature;and (4)the uplift of the air and the formation and development of the low-lever inversion.Besides,we did some sensitivity numerical experiments and discussed the effects of the radiation,the release of condensation latent heat and the change of soil moisture and temperature on the formation and development of fog.The success of numerical simulation experiment of fog has proved that the numerical forecasting of fog is promising.

An advection fog event response to future climate forcing in the 2030s-2080s:a case study for Shanghai

Fog may continue to inhibit industry in the future.Here,we focused on a specific advection fog event in Shanghai,China,and applied a pseudo global warming method to examine advection fog under the RCP8.5 highemission scenario.The method involved downscaling the future atmospheric conditions over the ensemble average of 19 global climate models from the fifth phase of the Coupled Model Intercomparison Project(CMIP5).We used the Weather Research and Forecasting Model coupled with a single-layer urban canopy model(WRF‒UCM)to run four sensitivity experiments and examined the advection fog and its relationship to changes in meteorological conditions.The results showed that:1)The advection fog event tended to remain in Shanghai despite global warming;2)advection fog will not change greatly in the future;however,the onset and dissipation times will change slightly;3)relative humidity(RH)locally increases prior to the onset of the advection fog,and decreases at the dissipating stage,despite the current and future experiments having the same RH initial and boundary conditions;4)a small increase in surface air temperature and an increase in RH contribute to the early advection fog onset,and vice versa.Windspeed facilitates the early onset and dissipation of advection fog.