scholarly journals Optical and Geometrical Properties of Cirrus Clouds over the Tibetan Plateau Measured by LiDAR and Radiosonde Sounding during the Summertime in 2014

2019 ◽  
Vol 11 (3) ◽  
pp. 302 ◽  
Author(s):  
Guangyao Dai ◽  
Songhua Wu ◽  
Xiaoquan Song ◽  
Liping Liu
Keyword(s):  
Tibetan Plateau ◽  
Optical Depth ◽  
Extinction Coefficient ◽  
Mean Value ◽  
Cirrus Clouds ◽  
The Tibetan Plateau ◽  
Convective Activity ◽  
Depolarization Ratio ◽  
Geometrical Properties ◽  
The Mean

Optical and geometrical characteristics of the cirrus clouds over Naqu (4508 m a.s.l., 31.48° N, 92.06° E), in the Tibetan Plateau were determined from LiDAR and radiosonde measurements performed during the third TIbetan Plateau EXperiment of atmospheric sciences (TIPEX III) campaign from July to August 2014. For the analysis of the temperature dependence, the simultaneous observations with LiDAR and radiosonde were conducted. Cirrus clouds were generally observed ranging from 5.2 km to 12 km above ground level (AGL) (i.e., 9.7 km to 16.5 km a.s.l.), with the midcloud temperatures ranging from −79.7 to −26.0 °C. The cloud thickness generally differed from 0.12 to 2.55 km with a mean thickness of 1.22 ± 0.70 km, and 85.7% of the measurement cases had thickness smaller than 1.5 km. The retrievals of linear particle depolarization ratio, extinction coefficient, and optical depth of cirrus clouds were provided. Moreover, the multiple scattering effect inside of cirrus clouds was corrected. The linear particle depolarization ratio of the cirrus clouds varied from 0.36 to 0.52, with a mean value of 0.44 ± 0.04. The optical depth of the cirrus clouds was between 0.01 and 3 following the scheme of Fernald-Klett method. Sub-visual, thin, and opaque cirrus clouds were observed at 4.76%, 61.90% and 33.34% of the measured cases, respectively. The temperature and thickness dependencies of the optical properties were studied in detail. A maximum cirrus thickness of around 2 km was found at temperatures between −60 and −50 °C. This study shows that the mean extinction coefficient of the cirrus clouds increases with the increase of temperature. Conversely, the measurements indicate that the linear particle depolarization ratio decreases with the increasing temperature. The relationships between the existence of cirrus clouds and the temperature anomaly (temperature difference from the mean value of the temperature during July and August 2014 over Naqu) and deep convective activity are also discussed. The formation of cirrus clouds is investigated and also its apparent relationship with the South Asia High Pressure, the dynamic processes of Rossby wave, and deep convective activity over the Tibetan Plateau. The outgoing longwave radiation of cirrus clouds is calculated with the Fu-Liou model and is shown to increases monotonously with the increase of optical depth.

scholarly journals Optical and Geometrical Properties of Cirrus Clouds over the Tibetan Plateau Measured by Lidar and Radiosonde Sounding at the Summertime in 2014

2017 ◽  
Author(s):  
Guangyao Dai ◽  
Songhua Wu ◽  
Xiaoquan Song ◽  
Liping Liu
Keyword(s):  
Tibetan Plateau ◽  
Optical Depth ◽  
Extinction Coefficient ◽  
Radiative Forcing ◽  
Mean Value ◽  
Cirrus Clouds ◽  
The Tibetan Plateau ◽  
Convective Activity ◽  
Depolarization Ratio ◽  
Geometrical Properties

Abstract. Optical and geometrical characteristics of cirrus clouds over Naqu (31.48° N,92.06° E), the Tibetan Plateau were determined from lidar and radiosonde measurements performed during the third TIbetan Plateau EXperiment of atmospheric sciences (TIPEX III) campaign from July to August 2014. For the analysis of the temperature dependence, the simultaneous observations by lidar and radiosonde were conducted. Cirrus clouds were generally observed ranging from 9.7 to 16.5 km above sea level (a.s.l.), with the cirrus middle temperatures in the range from −79.7 to −26.0 °C. The cloud thickness generally differed from 0.12 to 2.55 km with a mean thickness of 1.22 ± 0.70 km and 85.7 % of the case studies had thickness smaller than 1.5 km. The retrievals of linear particle depolarization ratio, extinction coefficient and optical depth of cirrus clouds were performed. Moreover, the multiple scattering effect inside of cirrus cloud was corrected. The linear particle depolarization ratio of the cirrus clouds varied from 0.36 to 0.52, with a mean value of 0.44 ± 0.037. The optical depth of all the cirrus clouds was between 0.01 and 3 following the scheme of Fernald-Klett method. Sub-visual, thin and opaque cirrus clouds were observed at 9.52 %, 57.14 % and 33.34 % of the measured cases, respectively. The temperature and thickness dependencies on optical properties were studied in detail. A maximum cirrus thickness of around 2 km was found at temperatures between −60 and −50 °C. This study shows that the cirrus mean extinction coefficient of the cirrus clouds increase with the increase of temperature. However, our measurements indicate that the linear particle depolarization ratio has the opposite change tendency along with temperature. The relationships between the presence of cirrus clouds and the temperature anomaly and deep convective activity are also discussed. The formation of cirrus clouds is also investigated and it has apparent relationship with the dynamic processes of Rossby wave and deep convective activity over the Tibetan Plateau. The cloud radiative forcing is calculated by Fu-Liou model and increases monotonously with the increase of optical depth.

scholarly journals Statistics of optical and geometrical properties of cirrus cloud over tibetan plateau measured by lidar and radiosonde

2018 ◽  
Vol 176 ◽  
pp. 05040
Author(s):  
Guangyao Dai ◽  
Songhua Wu ◽  
Xiaoquan Song ◽  
Xiaochun Zhai
Keyword(s):  
Tibetan Plateau ◽  
Hydrological Cycle ◽  
Regional Climate ◽  
Cirrus Clouds ◽  
Dynamic Processes ◽  
Cirrus Cloud ◽  
The Tibetan Plateau ◽  
Temperature Deviation ◽  
Geometrical Properties ◽  
Temperature Dependences

Cirrus clouds affect the energy budget and hydrological cycle of the earth’s atmosphere. The Tibetan Plateau (TP) plays a significant role in the global and regional climate. Optical and geometrical properties of cirrus clouds in the TP were measured in July-August 2014 by lidar and radiosonde. The statistics and temperature dependences of the corresponding properties are analyzed. The cirrus cloud formations are discussed with respect to temperature deviation and dynamic processes.

scholarly journals Optical and Geometrical Properties of Cirrus Clouds in Amazonia Derived From 1-year of Ground-based Lidar Measurements

2016 ◽  
Author(s):  
Diego A. Gouveia ◽  
Boris Barja ◽  
Henrique M. J. Barbosa ◽  
Theotônio Pauliquevis ◽  
Paulo Artaxo
Keyword(s):  
Optical Depth ◽  
Diurnal Cycle ◽  
High Frequency ◽  
Dry Season ◽  
Cirrus Clouds ◽  
Cloud Base ◽  
Wet Season ◽  
Geometrical Properties ◽  
Lidar Ratio ◽  
The Mean

Abstract. For one year, from July 2011 to June 2012, a ground-based raman lidar provided atmospheric observations north of Manaus, Brazil, at an experimental site (2.89° S and 59.97° W) for long-term aerosol and cloud measurements. Upper tropospheric cirrus clouds were observed more frequently than previous reports in tropical regions. The frequency of occurrence was found to be as high as 82 % during the wet season and not lower than 55 % during the dry season. The diurnal cycle shows a minimum around local noon and maximum during late afternoon, associated with the diurnal cycle precipitation. Optical and geometrical characteristics of these cirrus clouds were derived. The mean values were 14.4 ± 2.0 km (top), 12.7 ± 2.3 km (base), 1.7 ± 1.5 km (thickness), and 0.36 ± 1.20 (cloud optical depth). Cirrus clouds were found at temperatures down to –90 °C and 7 % were above the tropopause base. The vertical distribution was not uniform and two cloud types were identified: (1) cloud base > 14 km and optical depth ~0.02, and (2) cloud base < 14 km and optical depth ~0.2. A third type, not previously reported, was identified during the wet season, between 16 and 18 km with optical depth ~0.005. The mean lidar ratio was 20.2 ± 7.0 sr, indicating a mixture of thick plates and long columns. However, the clouds above 14 km have a bimodal distribution during the dry season with a secondary peak at about 40 sr suggesting that thin plates are a major habit. A dependence of the lidar ratio with cloud temperature (altitude) was not found, thus indicating they are well mixed in the vertical. Cirrus clouds classified as subvisible (τ < 0.03) were 40 %, whilst 37.7 % were thin cirrus (0.03 < τ < 0.3) and 22.3 % opaque cirrus (τ > 0.3). Hence, not only does the central Amazon have a high frequency of cirrus clouds, but a large fraction of subvisible cirrus clouds as well. This high frequency of subvisible cirrus clouds may contaminate aerosol optical depth measured by sun-photometers and satellite sensors to an unknown extent.

scholarly journals The Properties and Formation of Cirrus Clouds over the Tibetan Plateau Based on Summertime Lidar Measurements

2013 ◽  
Vol 70 (3) ◽  
pp. 901-915 ◽  
Author(s):  
Q. S. He ◽  
C. C. Li ◽  
J. Z. Ma ◽  
H. Q. Wang ◽  
G. M. Shi ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Large Scale ◽  
Longwave Radiation ◽  
Mean Value ◽  
Cirrus Clouds ◽  
The Tibetan Plateau ◽  
Mean Values ◽  
Upper Troposphere ◽  
Lidar Ratio ◽  
Highly Correlated

Abstract As part of the Tibet Ozone, Aerosol and Radiation (TOAR) project, a micropulse lidar was operated in Naqu (31.5°N, 92.1°E; 4508 m MSL) on the Tibetan Plateau to observe cirrus clouds continuously from 19 July to 26 August 2011. During the experiment, the time coverage of ice clouds only was 15% in the upper troposphere (above 9.5 km MSL). The cirrus top/bottom altitudes (mean values of 15.6/14.7 km) are comparable to those measured previously at tropical sites but relatively higher than those measured at midlatitude sites. The majority of the cloud layers yielded a lidar ratio between 10 and 40 sr, with a mean value of 28 ± 15 sr, characterized by a bimodal frequency distribution. Subvisible, thin, and opaque cirrus formation was observed in 16%, 34%, and 50% of all cirrus cases, respectively. A mean cirrus optical depth of 0.33 was observed over the Tibetan Plateau, slightly higher than those in the subtropics and tropics. With decreasing temperature, the lidar ratio increased slightly, whereas the mean extinction coefficient decreased significantly. The occurrence of clouds is highly correlated with the outgoing longwave radiation and the strong cold perturbations in the upper troposphere. Deep convective activity and Rossby waves are important dynamical processes that control cirrus variations over the Tibetan Plateau, where both anvil cirrus outflowing from convective cumulonimbus clouds and large-scale strong cold perturbations in the upper troposphere should play an important role in cirrus formation.

scholarly journals The role of ASM on the formation and properties of cirrus clouds over the Tibetan Plateau

Tellus B ◽  
2019 ◽  
Vol 71 (1) ◽  
pp. 1577070 ◽  
Author(s):  
Qianshan He ◽  
Xiangdong Zheng ◽  
Jian Li ◽  
Wei Gao ◽  
Yanyu Wang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Cirrus Clouds ◽  
The Tibetan Plateau

Developing the soil texture effects on the surface resistance to bare soil based on MOD16 algorithm to estimate evapotranspiration over the Tibetan Plateau

2020 ◽  
Author(s):  
Ling Yuan ◽  
Yaoming Ma ◽  
Xuelong Chen
Keyword(s):  
Tibetan Plateau ◽  
Soil Texture ◽  
Land Surface ◽  
Bare Soil ◽  
The Other ◽  
Accurate Estimation ◽  
Surface Model ◽  
The Tibetan Plateau ◽  
The Mean ◽  
Modified Algorithm

&lt;p&gt;Evapotranspiration (ET), composed of evaporation (ETs) and transpiration (ETc) and intercept water (ETw), plays an indispensable role in the water cycle and energy balance of land surface processes. A more accurate estimation of ET variations is essential for natural hazard monitoring and water resource management. For the cold, arid, and semi-arid regions of the Tibetan Plateau (TP), previous studies often overlooked the decisive role of soil properties in ETs rates. In this paper, an improved algorithm for ETs in bare soil and an optimized parameter for ETc over meadow based on MOD16 model are proposed for the TP. The nonlinear relationship between surface evaporation resistance (r&lt;sub&gt;s&lt;/sub&gt;&lt;sup&gt;s&lt;/sup&gt;) and soil surface hydration state in different soil texture is redefined by ground-based measurements over the TP. Wind speed and vegetation height were integrated to estimate aerodynamic resistance by Yang et al. (2008). The validated value of the mean potential stomatal conductance per unit leaf area (C&lt;sub&gt;L&lt;/sub&gt;) is 0.0038m s&lt;sup&gt;-1&lt;/sup&gt;. And the algorithm was then compared with the original MOD16 algorithm and a soil water index&amp;#8211;based Priestley-Taylor algorithm (SWI&amp;#8211;PT). After examining the performance of the three models at 5 grass flux tower sites in different soil texture over the TP, East Asia, and America, the validation results showed that the half-hour estimates from the improved-MOD16 were closer to observations than those of the other models under the all-weather in each site. The average correlation coefficient(R&lt;sup&gt;2&lt;/sup&gt;) of the improved-MOD16 model was 0.83, compared with 0.75 in the original MOD16 model and 0.78 in SWI-PT model. The average values of the root mean square error (RMSE) are 35.77W m&lt;sup&gt;-2&lt;/sup&gt;, 79.46 W m&lt;sup&gt;-2&lt;/sup&gt;, and 73.88W m&lt;sup&gt;-2&lt;/sup&gt; respectively. The average values of the mean bias (MB) are -4.08W m&lt;sup&gt;-2&lt;/sup&gt;, -52.36W m&lt;sup&gt;-2&lt;/sup&gt;, and -11.74 W m&lt;sup&gt;-2&lt;/sup&gt; overall sites, respectively. The performance of these algorithms are better achieved on daily (R&lt;sup&gt;2&lt;/sup&gt;=0.81, RMSE=17.22W m&lt;sup&gt;-2&lt;/sup&gt;, MB=-4.12W m&lt;sup&gt;-2&lt;/sup&gt;; R&lt;sup&gt;2&lt;/sup&gt;=0.64, RMSE=56.55W m&lt;sup&gt;-2&lt;/sup&gt;, MB=-48.74W m&lt;sup&gt;-2&lt;/sup&gt;; R2=0.78, RMSE=22.3W m&lt;sup&gt;-2&lt;/sup&gt;, MB=-9.82W m&lt;sup&gt;-2&lt;/sup&gt;) and monthly (R2=0.93, RMSE=23.35W m&lt;sup&gt;-2&lt;/sup&gt;, MB=-2.8W m&lt;sup&gt;-2&lt;/sup&gt;; R2=0.86, RMSE=69.11W m&lt;sup&gt;-2&lt;/sup&gt;, MB=-39.5W m&lt;sup&gt;-2&lt;/sup&gt;; R2=0.79, RMSE=62.8W m&lt;sup&gt;-2&lt;/sup&gt;, MB=-9.7W m&lt;sup&gt;-2&lt;/sup&gt;) scales. Overall, the results showed that the newly developed MOD16 model captured ET more accurately than the other two models. The comparisons between the modified algorithm and two mainstream methods suggested that the modified algorithm could produce high accuracy ET over the meadow sites and has great potential for land surface model improvements and remote sensing ET promotion for the ET region.&lt;/p&gt;

scholarly journals Statistics of vertical backscatter profiles of cirrus clouds

2011 ◽  
Vol 11 (24) ◽  
pp. 12925-12943 ◽  
Author(s):  
P. Veglio ◽  
T. Maestri
Keyword(s):  
Optical Depth ◽  
Satellite Observation ◽  
Cirrus Clouds ◽  
Cloud Base ◽  
Physical Parameters ◽  
Cloud Optical Depth ◽  
Cloud Temperature ◽  
The Mean ◽  
Depth Increase ◽  
The Impact

Abstract. A nearly global statistical analysis of vertical backscatter and extinction profiles of cirrus clouds collected by the CALIOP lidar, on-board of the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation, is presented. Statistics on frequency of occurrence and distribution of bulk properties of cirrus clouds in general and, for the first time, of horizontally homogeneous (on a 5-km field of view) cirrus clouds only are provided. Annual and seasonal backscatter profiles (BSP) are computed for the horizontally homogeneous cirri. Differences found in the day/night cases and for midlatitudes and tropics are studied in terms of the mean physical parameters of the clouds from which they are derived. The relationship between cloud physical parameters (optical depth, geometrical thickness and temperature) and the shape of the BSP is investigated. It is found that cloud geometrical thickness is the main parameter affecting the shape of the mean CALIOP BSP. Specifically, cirrus clouds with small geometrical thicknesses show a maximum in mean BSP curve located near cloud top. As the cloud geometrical thickness increases the BSP maximum shifts towards cloud base. Cloud optical depth and temperature have smaller effects on the shape of the CALIOP BSPs. In general a slight increase in the BSP maximum is observed as cloud temperature and optical depth increase. In order to fit mean BSPs, as functions of geometrical thickness and position within the cloud layer, polynomial functions are provided. The impact on satellite radiative transfer simulations in the infrared spectrum when using either a constant ice-content (IWC) along the cloud vertical dimension or an IWC profile derived from the BSP fitting functions is evaluated. It is, in fact, demonstrated that, under realistic hypotheses, the mean BSP is linearly proportional to the IWC profile.

scholarly journals The Characteristics of the Aerosol Optical Depth within the Lowest Aerosol Layer over the Tibetan Plateau from 2007 to 2014

2018 ◽  
Vol 10 (5) ◽  
pp. 696 ◽  
Author(s):  
Miao Zhang ◽  
Lunche Wang ◽  
Muhammad Bilal ◽  
Wei Gong ◽  
Ziyue Zhang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Aerosol Optical Depth ◽  
Optical Depth ◽  
Aerosol Layer ◽  
The Tibetan Plateau
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