| The optical parameters of high cloud and aerosol, over Lanzhou and its nearby regions with complicated topography, are probed by using lidar measurement. In order to indicate the influence of high cloud and the radiative effect of aerosol on the urban boundary layer, numerical simulation and theoretical analysis are implemented by coupling the WRF model and ABL model in which the influence of high cloud and the radiative effect of aerosol are considered.(1) This paper brings forward the detailed lidar measurement schemes on observing high cloud and aerosol over Lanzhou, including the determination of calibration altitude and boundary condition, as well as the ration of extinction to backscatter of high cloud and aerosol. Preliminary analysis on the collected data indicates a good consistence between the extinction coefficient measured by lidar and vertical profile of the relative humidity retrieved by radiometrics profiling radiometor, both with maximum values located within the cloud and at the low level of the atmosphere. The extinction coefficient and relative humidity increase with height from low level to 2 km and then decrease with height, suggesting that the aerosol layer is located below 2 km.(2) The WRF is utilized to simulate basic meteorological fields in winter over the valley basin city Lanzhou. Through comparison and analysis, results of the simulation are found to be generally consistent with the present theories and observations. High-resolution WRF runs operate with high stability and can sufficiently simulate the characteristics of the atmospheric boundary layer. Further, High-resolution WRF runs can also offer the ABL model with reasonable time-varying lateral boundary conditions.(3) The high cloud decreases the aerosol heating rate under its floating layer in the daytime. The difference between high cloud and cloudless weather is obvious at 12:00 on the altitude of 50m. The peak value of difference is 0.109 K/h. This high cloud will also decrease the surface heating rate which is changed with time and the peak value is about 0.089 K/h at 16:00. At night, the high cloud emits long wave radiation itself and reflects the surface long wave radiation, which leads to weaken the aerosol cooling characteristics, and the peak value is about 0.033 K/h at 03:00 on altitude of 1500m. (4) The WRF and ABL model are coupled reasonably, and the data is incorporated to simulate the structure characteristics of the ABL under the influence of the radiative effect of high clouds and aerosols. The atmosphere sustains such kind of circulation, with weak upward motion in the basin and along the southern slope of the mountain during daytime, but with downward motion along all the slopes during night time. The model can well present the corporation of the urban heat island effect and valley wind circulation.(5) The influence of high cloud radiative effect on the boundary layer structure is extracted from the combination effects of high cloud and aerosol, using numerical experiments. The forcing intensity of aerosol radiative effect on ABL is analyzed with the existence of high clouds, as well as to what extent the combination effect of high cloud and aerosol influence the ABL after 5 hours of their corporation.At night, high clouds lead to low level (above 900m) temperature increase by 0.1K to 0.8K and wind speed enhancement by 0.02m/s～0.2m/s at the layer below 500m. But over 600m, high clouds decrease the wind speed by 0.02～0.25m/s. Aerosol leads to temperature decrease above 100m, but high cloud make the cooling degree decrease. The combined radiative effect of high cloud and aerosol induce surface temperature increase of 1.5K, but temperature decrease of 0.2K～0.7K above 100 m. The existence of high cloud and aerosol leads the wind speed within ABL to decrease by 0.03m/s～0.025m/s at the layer below 300m, and by 0.03m/s～0.1m/s above 600m.During daytime, temperature decreases by 0.2K～0.3K below 1000 m but increases by 0.2K～0.35K, under the effect of high cloud. Below 500m, wind speed increases by 0.01m/s～0.05m/s causing by the high cloud radiative effect, but decreases by 0.01m/s～0.35m/s under the combined radiative effect of high clouds and aerosols. The combined action of high cloud and aerosol also results in surface temperature decrease of 1.3K and wind speed increase of 0.1m/s～0.12m/s above 500m. But at the heating layer induced by the aerosol (above 200m), temperature tends to increase, with its maximum increasing value of 0.85K at 500m.
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