Evaluation of cloud base height measurements from Ceilometer CL31 and MODIS satellite over Ahmedabad, India

Som Sharma,Rajesh Vaishnav,Munn V Shukla,Pradeep K Thapliyal,Prashant Kumar,Prateek Kumar,Shyam Lal,Yashwant B Acharya

doi:10.5194/amt-9-711-2016

Abstract

Abstract. Clouds play a tangible role in the Earth's atmosphere and in particular, the cloud base height (CBH), which is linked to cloud type, is one of the most important characteristics to describe the influence of clouds on the environment. In the present study, CBH observations from Ceilometer CL31 were extensively studied during May 2013 to January 2015 over Ahmedabad (23.03° N, 72.54° E), India. A detailed comparison has been performed with the use of ground-based CBH measurements from Ceilometer CL31 and CBH retrieved from MODIS (Moderate Resolution Imaging Spectroradiometer) onboard Aqua and Terra satellite. CBH retrieved from MODIS is ∼ 1.955 and ∼ 1.093 km on 25 July 2014 and 1 January 2015 respectively, which matches well with ceilometer-measured CBH ( ∼ 1.92 and ∼ 1.097 km). Some interesting features of cloud dynamics viz. strong downdraft and updraft have been observed over Ahmedabad which revealed different cloud characteristics during monsoon and post-monsoon periods. CBH shows seasonal variation during the Indian summer monsoon and post-monsoon period. Results indicate that the ceilometer is an excellent instrument to precisely detect low- and mid-level clouds, and the MODIS satellite provides accurate retrieval of high-level clouds over this region. The CBH algorithm used for the MODIS satellite is also able to capture the low-level clouds.

Highlights

Clouds, visible masses of tiny water droplets or frozen ice crystals, are one of the most crucial parameters for weather and climate prediction (Bauer et al, 2011; Errico et al, 2007; Shah et al, 2010). Kiehl and Trenberth (1997) showed the importance of clouds on the global energy budget
The present study focuses on the most important features of temporal variability of cloudiness over Ahmedabad during May 2013 to January 2015, using cloud data retrieved from the MODIS satellite, in conjunction with cloud observations by the ceilometer
This study investigates cloud analysis over the Ahmedabad region using ceilometer measurements and MODIS satellite-retrieved cloud parameters

Summary

Introduction

Visible masses of tiny water droplets or frozen ice crystals, are one of the most crucial parameters for weather and climate prediction (Bauer et al, 2011; Errico et al, 2007; Shah et al, 2010). Kiehl and Trenberth (1997) showed the importance of clouds on the global energy budget. Kiehl and Trenberth (1997) showed the importance of clouds on the global energy budget. Randall et al (1984) observed that a 4 % increase in the cloud cover with stratocumulus can compensate the global warming due to CO2 doubling. Koren et al (2010) discussed that aerosols affect clouds, which contributes to climate change. Kokhanovsky et al (2007) discussed that the global cloud top height (CTH) is near to 6000 m. Varikoden et al (2011) studied cloud base height (CBH) over Thiruvananthapuram (8.4◦ N, 76.9◦ E), India, during different seasons and found diurnal and seasonal variations except rainy days. Zhang et al (2010) deployed AMF (ARM Mobile Facility) for radiosondes in Shouxian, China, and showed that the diurnal variation in upper-level clouds thickness is larger than that of low-level clouds over this region The types of low-level clouds and their development are governed by meteorological conditions, especially in the atmospheric boundary layer, such as vertical stability (Norris, 1998). Koren et al (2010) discussed that aerosols affect clouds, which contributes to climate change. Andrejczuk et al (2014) found that cloud albedo may increase as a result of the seeding, if enough aerosols are delivered into the cloud. Kokhanovsky et al (2007) discussed that the global cloud top height (CTH) is near to 6000 m. Li and Min (2010) showed the impact of mineral dust on tropical clouds which is dependable on rain type. Varikoden et al (2011) studied cloud base height (CBH) over Thiruvananthapuram (8.4◦ N, 76.9◦ E), India, during different seasons and found diurnal and seasonal variations except rainy days. Zhang et al (2010) deployed AMF (ARM Mobile Facility) for radiosondes in Shouxian, China, and showed that the diurnal variation in upper-level clouds thickness is larger than that of low-level clouds over this region

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