Influence of assimilating ground-based microwave radiometer data into the WRF model on precipitation

Ground-based microwave radiometers profilers(MWRPs)have been used in numerical weather prediction(NWP)systems and show different impacts on forecasts.Currently,there are around hundreds of ground-based MWPRs used in weather stations over China;however,the application of MWPRs in NWP systems is rather limited.In this work,two MWRP retrieved profiles were assimilated into the Weather Research and Forecasting(WRF)model for a rainstorm event that occurred in Beijing,China.The quality of temperature and humidity profiles retrieved from the MWRP was evaluated against radiosonde observations and showed the reliability of the two MWRP products.Then,comparisons between the measurements of ground-based rain gauges and the corresponding forecasted precipitation in different periods of the rainstorm were investigated.The results showed that assimilating the two MWRPs affected the distribution and intensity of rainfall,especially in the early stage of the rainstorm.With the development of the rainstorm,adding MWRP data showed only a slight influence on the precipitation during the stable and mature period of the rainstorm,since the two MWRP observations were too limited to affect the large area of heavy rainfall.

0-10 KM TEMPERATURE AND HUMIDITY PROFILES RETRIEVAL FROM GROUND-BASED MICROWAVE RADIOMETER

Deviation exists between measured and simulated microwave radiometer sounding data. The bias results in low-accuracy atmospheric temperature and humidity profiles simulated by Back Propagation artificial neural network models. This paper evaluated a retrieving atmospheric temperature and humidity profiles method by adopting an input data adjustment-based Back Propagation artificial neural networks model. First, the sounding data acquired at a Nanjing meteorological site in June 2014 were inputted into the Mono RTM Radiative transfer model to simulate atmospheric downwelling radiance at the 22 spectral channels from 22.234 GHz to 58.8 GHz, and we performed a comparison and analysis of the real observed data; an adjustment model for the measured microwave radiometer sounding data was built. Second, we simulated the sounding data of the 22 channels using the sounding data acquired at the site from 2011 to 2013. Based on the simulated rightness temperature data and the sounding data, BP neural network-based models were trained for the retrieval of atmospheric temperature, water vapor density and relative humidity profiles. Finally, we applied the adjustment model to the microwave radiometer sounding data collected in July 2014, generating the corrected data. After that, we inputted the corrected data into the BP neural network regression model to predict the atmospheric temperature, vapor density and relative humidity profile at 58 high levels from 0 to 10 km. We evaluated our model's effect by comparing its output with the real measured data and the microwave radiometer's own second-level product. The experiments showed that the inversion model improves atmospheric temperature and humidity profile retrieval accuracy; the atmospheric temperature RMS error is between 1 K and 2.0 K; the water vapor density's RMS error is between 0.2 g/m^3 and 1.93 g/m3; and the relative humidity's RMS error is between 2.5% and 18.6%.

Primary Analysis of Sounding Data from a Multi-channel Parallel Ground-based Microwave Radiometer

The sounding data of a multi-channel parallel ground-based microwave radiometer （MWR） in Fuzhou station in July and August in 2016 were compared with the sounding data of a radiosonde in the same position in the same period. The results showed that the correlations between the two types of temperature or humidity detected by the microwave radiometer and the radiosonde were significant at 0.05 level, indicating that the overall changing trends of temperature or humidity detected by the two devices were similar. The temperature detected by the microwave radiometer and the radiosonde decreased with the increase of height. The difference between the changes in the height of the zero layer detected by the micro- wave radiometer and the radiosonde was not significant, and their trends were basically the same.

Improving Satellite-Retrieved Cloud Base Height with Ground-Based Cloud Radar Measurements

Cloud base height(CBH) is a crucial parameter for cloud radiative effect estimates, climate change simulations, and aviation guidance. However, due to the limited information on cloud vertical structures included in passive satellite radiometer observations, few operational satellite CBH products are currently available. This study presents a new method for retrieving CBH from satellite radiometers. The method first uses the combined measurements of satellite radiometers and ground-based cloud radars to develop a lookup table(LUT) of effective cloud water content(ECWC), representing the vertically varying cloud water content. This LUT allows for the conversion of cloud water path to cloud geometric thickness(CGT), enabling the estimation of CBH as the difference between cloud top height and CGT. Detailed comparative analysis of CBH estimates from the state-of-the-art ECWC LUT are conducted against four ground-based millimeter-wave cloud radar(MMCR) measurements, and results show that the mean bias(correlation coefficient) is0.18±1.79 km(0.73), which is lower(higher) than 0.23±2.11 km(0.67) as derived from the combined measurements of satellite radiometers and satellite radar-lidar(i.e., Cloud Sat and CALIPSO). Furthermore, the percentages of the CBH biases within 250 m increase by 5% to 10%, which varies by location. This indicates that the CBH estimates from our algorithm are more consistent with ground-based MMCR measurements. Therefore, this algorithm shows great potential for further improvement of the CBH retrievals as ground-based MMCR are being increasingly included in global surface meteorological observing networks, and the improved CBH retrievals will contribute to better cloud radiative effect estimates.

Microwave Brightness Temperature and Lunar Soil Dielectric Property Retrieve

Among many scientific objectives of lunar exploration, investigations on lunar soil become more and more attractive to the scientists duo to the existence of abundant 3He and ilmenite in the lunar soil and their possible utilization. Although the soil composition determination on the lunar surface is available by visible light spectrometer,γ/X-ray spectrometer etc, the evaluations on the total reserves of 3He and ilmenite in the lunar deep and on the thickness of the lunar soil are still impossible so far. In this paper, the authors first give a rough analysis of the microwave brightness temperature images of the lunar disc observed using the NRAO 12 Meter Telescope and Siberian Solar Radio Telescope; then introduce our researches on the microwave dielectric properties of lunar soil simulators; finally, discuss some basic relations between the microwave brightness temperature and lunar soil properties.

Ground-based investigations on phase-moving phenomenon with space sublimation cooling for lunar exploration missions

The lunar surface is a typical vacuum environment,and its harsh heat rejection conditions bring great challenges to the thermal control technology of the exploration mission.In addition to the radiator,the sublimator is recommended as one of the promising options for heat rejection.The sublimator makes use of water to freeze and sublimate in a porous medium,rejecting heat to the vacuum environment.The complex heat and mass transfer process involves many physical phenomena such as the freezing and sublimation phase change of water in the porous medium and the movement of the phase-change interface.In this paper,the visualized ground-based experimental approaches of space sublimation cooling were presented to reveal the moving law of threephase point and the growth phenomenon of ice-peak and icicle in microchannels under vacuum conditions.The visualized experiments and results prove that the freezing ice is divided into the porous ice-peak and the transparent icicle.As the sublimation progresses,the phase-change interface moves downward steadily,the length of the ice-peak increases,but the icicle decreases.The visualized experiments of space sublimation cooling in the capillary have guiding significance to reveal the sublimation cooling mechanism of water in the sublimator for lunar exploration missions.

利用微波辐射计对月壤厚度进行研究

介绍了运用并矢Green函数和起伏逸散定理来计算平面分层媒质的辐射亮温,同时利用最小二乘法对多通道辐射计的模拟测量结果进行处理得到分层媒质厚度的方法。将该方法应用于月壤厚度的反演研究,在假定月壤如平面分层结构模型的情况下,得到了其厚度的反演结果,并对反演误差原因进行分析。

非均匀多层月壤微波辐射传输模型与亮温模拟

研究月表物质的微波辐射和传输特性、建立合理的月壤厚度反演模型,对估计月壤厚度有重要意义。综合考虑影响亮温的主要因素随月壤厚度的变化,提出了一种非均匀精细分层的多层月壤模型。随后,应用该模型对CE-1号上微波辐射计四个通道获得的亮度温度随时间、地理位置和月壤厚度的变化进行了模拟和分析,并与其他模型和方法进行了比较。比较结果表明,该非均匀精细分层模型具有计算量小、稳定性好的优点。

Diviner红外温度与嫦娥卫星微波探测仪月表亮温的比较分析

提出使用高分辨率的Diviner辐射计红外温度作为月壤热传导的边界输入条件,使得月壤物理温度廓线的模拟更接近月表真实情况.利用Diviner物理温度廓线模拟的微波亮温与嫦娥二号卫星微波探测仪(CELMS2)的实测亮温匹配,来分析CELMS2数据的有效性和稳定性,为月壤微波特性的反演奠定基础.以哥白尼坑区域为例,对比分析了Diviner辐射计红外通道温度与CELMS1实测微波亮温的变化趋势.选择月球虹湾地区内一位置点(45.1°-45.5°N,33.1°-33.5°W),分析了CELMS2在该位置点内5个月球时刻的亮温数据.通过对实测亮温与模拟亮温在经纬度和太阳高度角的匹配分析得到,在高频微波通道内两者的相关性达到96%以上,表明嫦娥二号微波探测仪亮温数据具有较高的稳定性,可以为月壤特性反演研究提供可靠数据来源.

地基月球自动观测辐射仪的跟踪系统设计

近年来月球辐照度的地基观测实验不断增加,为了满足地基对月球辐射高精度、高频次的观测,需要设计高精度的月球自动跟踪系统进行跟踪实验。所设计跟踪系统通过月球位置算法获得月球的天顶角和方位角进行视月跟踪,然后采用以四象限探测器为核心器件的光电跟踪来精确跟踪月球。经外场跟踪实验验证,视月跟踪和光电跟踪相结合具有高精度的跟踪效果,跟踪精度在±0.2°以内,表明跟踪系统具有较高的准确性和可靠性。

China's Space Exploration

In this report the author outlines China’s space exploration to date,describes plans for the next decade and proposes a framework for international cooperation in the exploration of

Simulations of lunar equatorial regolith temperature profile based on measurements of Diviner on Lunar Reconnaissance Orbiter

Lunar equatorial regolith temperature profiles were simulated using the half-limited solid heat conduction model. Based on the infrared data measured using the Diviner radiometer on the Lunar Reconnaissance Orbiter launched by the United Sates in June 2009, three factors influencing temperature profiles were analyzed. The infrared brightness temperature data from Diviner channel 7 were used to retrieve surface temperature. In simulating regolith temperature profiles, the retrieved temperature, rather than temperatures calculated from solar radiance at the lunar surface, were used as the input for surface temperature in solving the heat-conductive equation. The results showed that the bottom-layer temperature at depths of 6 m approached almost 246 K after 10000 iterations. The temperature was different to the temperature of 250 K at the same depth encountered in simulations using solar radiance. Simulations from both methods of surface temperatures over a lunar day gave similar variations. At lunar night, the temperature difference between the two was about 2 K; the main differences occurred when the solar elevation angle was very low when surface temperatures are largely affected by terrain topography. With no certainty in lunar temperature profiles at present, the advantage of the retrieval method using infrared sensor data as input to the boundary conditions in solving the lunar heat conduction equation is that simulations of surface temperature variations are more accurate. This is especially true in areas with large variations in terrain topography, where surface temperatures vary greatly because of shading from the sunlight.

嫦娥五号等着陆区的月壤微波热辐射特性及地质意义分析

嫦娥三、四和五号的原位月壤探测为基于嫦娥一、二号卫星微波辐射计数据的月球科学研究提供了重要参考.本文基于嫦娥二号卫星微波辐射计数据,生成了着陆区亮温图;为了消除亮温随纬度变化的影响,突出亮温与月壤成分之间的关系,定义和制作了规则亮温图和亮温差图;基于Kaguya MI数据,制作了研究区氧化亚铁、氧化钛、单斜辉石和橄榄石含量图;结合原位月壤探测成果,系统分析了嫦娥三、四和五号着陆区月壤的微波热辐射特性.主要研究发现包括以下三点:(1)嫦娥五号着陆区具有稳定的亮温表现,表明该地区月壤成分随深度的变化不明显,可以作为微波热辐射异常研究的重要参考;(2)嫦娥三号着陆区微波数据探测范围内月壤存在分层结构,以低频数据为代表的深层、以高频数据探测为代表的浅层和以可见光成果为代表的表层,成分变化很大;(3)在嫦娥四号着陆区发现并提出了微波冷异常的存在,并初步分析了微波冷异常的成因机制.研究发现,微波辐射计数据可用于月海玄武岩的识别,可以为深化未来的月海岩浆演化研究提供重要的科学参考.