C.Fairall, L.Bariteau, D. Wolfe, A.Grachev and W.Otto September, 2006 Readme for the data files from the 2006 Texas Air Quality Study (TexAQS) and Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS) aboard the NOAA Ship Ronald H. Brown. This document is a description of the different ceilometer data files where the following notation has been used: - JD for Julian day. - MM, DD and YY for month, day and year respectively. A. Raw data There are two output files for the ceilometer, and they are located in the folder called TexAQS_2006\RHB\ceilometer\Raw. The .dat files are the raw hexadecimal data, and the .sta files contain the status of the ceilometer during its operation. B. “Processed” data A program was used to reformat the raw data into user friendly files: • JD_MM_DD_YY.txt is the conversion of the raw hexadecimal data into ASCII format. 1 N, where N=number of cloud layers (0-3) or a code (4-5) for marginal clouds 2 Height of the first layer in meters (NaN unless N>0) 3 Height of the second layer in meters (NaN unless N>1) 4 Height of the third layer in meters (NaN unless N>2) 5 Hour 6 Min 7 Sec • backscatter_JD_MM_DD_YY.mat is raw variables saved into a binary MAT-file form. To retrieve the data, use the load function of Matlab. 1 Time in decimal hours 2 Range of each gate in meters 3 Sensitivity normalized backscatter coefficient in the units 10-7.srad-1.m-1 These files are saved in the folder TexAQS_2006\RHB\ceilometer\Processed. C. Processed images From the binary MAT-files, daily graphs have been produced. These plots can be found in the folder TexAQS_2006\RHB\ceilometer\Processed_Images. • TEXAQS2006_ceilometer_JD_MM_DD_YY_backscatter.jpg is the time-height color plot of the ceilometer backscatter. • TEXAQS2006_ceilometer_JD_MM_DD_YY _base.jpg is the time-height plot of the cloud base. D. Processed data The final files of our process are the files Texaqs06_ceilo_time.txt where time = 30s, 10-min or 1-hr. The program Dana_ceilo7_rhb_Texaqs06.m was run to process raw ceilometer daily files (JD_MM_DD_YY.txt). This program reads all available files and writes a new file (Texaqs06_ceilo_30s.txt) that contains the basic cloud base height information: 1 Julian date 2 N, where N=number of cloud layers (0-3) or a code (4-5) for marginal clouds 3 Height of the first layer in meters (NaN unless N>0) 4 Height of the second layer in meters (NaN unless N>1) 5 Height of the third layer in meters (NaN unless N>2) The program then computes cloud statistics at 10-min and 60-min time resolution. New files are written on these statistics with the following data columns. The data files Texaqs06_ceilo_10min.txt and Texaqs06_ceilo_1hr.txt are: 1 Julian date 2 Number of samples 3 Number of clear samples 4 Number of one cloud layer samples 5 Number of multiple cloud layer samples 6 Number of samples with N=4, obscured 7 Number of samples with N=5, partially obscured 8 Clear fraction 9 Cloudy fraction 10 Cloudy fraction including obscured 11 Median cloud height (m) 12 Height with 16% clouds lower 13 Height with 16% clouds higher You can find these files either in the folder TexAQS_2006\RHB\ceilometer or in TexAQS_2006\RHB\Scientific_analysis\Ceilo.