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This README describes data-set of polluted cloud tracks.
Additional information
Heido Trofimov heidot@ut.ee
Velle Toll velle.toll@ut.ee

This work is funded by the Estonian Research Council personal research funding grant PSG202.
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DATASET
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The dataset contains positions and time of occurrence of polluted cloud tracks. 
The locations of polluted cloud tracks in MODIS satellite images have been hand-logged 
at various anthropogenic and natural aerosol sources over land and ocean.

The dataset can be used to study impact of aerosols on clouds.

Creators: Heido Trofimov, Velle Toll
Organisation: University of Tartu
Rights-holder: University of Tartu
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TERMS OF USE
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Copyright 2019 University of Tartu. 
This dataset is licensed by the rights-holder under a Creative Commons Attribution 4.0 International Licence: https://creativecommons.org/licenses/by/4.0/.
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CONTENTS
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The folder POLLUTION_TRACKS contains txt files with locations of
polluted clouds and MODIS observation times.

The file Norilsk.txt contains only MODIS observation times for the
city of Norilsk, situated at 69°20′N 88°13′E

The file Non-Norilsk.txt contains MODIS observation times, which are followed by
the longitude and latitude of the polluted cloud track, which were calculated
as the average values of hand-logged coordinates of the pollution tracks.

MODIS TIME STAMPS
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SATYYYYDDD.HHMM

SAT is platform with MODIS intstrument. MOD is Terra and MYD is Aqua.
YYYY is year.
DDD is Julian day of year. Note that years 2000, 2004, 2008, 2012, 2016 are leap years.
HH is hour.
MM is minute.

All times are UTC time, not local time.
The time stamp defines the name of MODIS file/granule what contains sampled track.
The given time is time of acquisition.
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COORDINATES
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Track centre lines for Non-Norilsk cases are defined by a WGS84 longitude-latitude  pair.
WGS84 longitude is given in the first column and latitude in the second column.

Example:
SATYYYYDDD.HHMM
lon lat
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METHOD and PROCESSING
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The locations of polluted cloud tracks have been hand-logged in the MODIS satellite images. 
Near-infrared composite images from National Aeronautics and Space Administration (NASA) Global Imagery Browse Services are utilized for visually finding the pollution tracks. 
The 2.1 μm near-infrared signatures resulting from increased cloud droplet number concentrations are used to visually identify polluted cloud tracks.
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