Aqua and SST NC dataset questions
Posted: Tue Apr 06, 2021 5:25 am America/New_York
Hello. I am working with the aqua mapped NC files in order to measure the levels of chlor_a in the ocean. I am also working with SST NC files. I have made some observations that I require feedback on please:
1 - LAT AND LON VARIATION. I compared the annual aqua chlor_a NC files from 2019 and 2020, and they both have the same increment variations between lat and lon index positions (where the difference between adjacent positions is not the same). While most of these increments can be truncated to .041666, there are outliers. Is this expected? Here is a printout from my console:
Number of different GPS increments in Chlor 2019 : 14
[0.041656494, 0.04166412353515625, 0.04166603088378906, 0.041666507720947266, 0.041666626930236816, 0.041666656732559204, 0.0416666641831398, 0.0416666679084301, 0.0416666716337204, 0.04166668653488159, 0.04166674613952637, 0.04166698455810547, 0.041667938232421875, 0.0416717529296875]
Number of different GPS increments in Chlor 2020 : 14
[0.041656494, 0.04166412353515625, 0.04166603088378906, 0.041666507720947266, 0.041666626930236816, 0.041666656732559204, 0.0416666641831398, 0.0416666679084301, 0.0416666716337204, 0.04166668653488159, 0.04166674613952637, 0.04166698455810547, 0.041667938232421875, 0.0416717529296875]
The increments from both data sets are equal.
2 - SST SPREAD. In the annual SST file for 2020, I noticed that the areas of inland water such as lakes and rivers seem larger than they are in reality. Has any 'spread' occurred during the creation of these files that would make values leak out of the real world boundaries of these bodies of water?
3 - SPIKE CHLOR ANOMALY. In the monthly aqua NC files for 2020, I noticed a spike in the chlor_a value for a particular point during the month of February. The spike was approx 98.8. However, the mode for the remainder of the year was only 3.3 approx. I investigated further by analyzing the daily data for this point for February. There was only 1 valid data point - the 16th of February. To verify, I ran the same check for all points adjoining the original point, and they had the same singular high value on the 16th. Has data corruption occurred at this point? The point is just off the coast of Brisbane, Australia. I also noticed that the annual value for this point was listed as 98.8, which is not the average over the course of the year. What type of algorithm is being using to determine which values to show on the annual data sets? Is the scale of 0 to 100 for chlor_a the true chlor value in MG or has some other factor been applied to it?
4 - I am processing many data files as part of my study. Does NASA have a public facing REST API, or similar, that allows me to read directly from the Aqua chlor and SST databases in a more flexible way, rather than having to download and process NC data?
1 - LAT AND LON VARIATION. I compared the annual aqua chlor_a NC files from 2019 and 2020, and they both have the same increment variations between lat and lon index positions (where the difference between adjacent positions is not the same). While most of these increments can be truncated to .041666, there are outliers. Is this expected? Here is a printout from my console:
Number of different GPS increments in Chlor 2019 : 14
[0.041656494, 0.04166412353515625, 0.04166603088378906, 0.041666507720947266, 0.041666626930236816, 0.041666656732559204, 0.0416666641831398, 0.0416666679084301, 0.0416666716337204, 0.04166668653488159, 0.04166674613952637, 0.04166698455810547, 0.041667938232421875, 0.0416717529296875]
Number of different GPS increments in Chlor 2020 : 14
[0.041656494, 0.04166412353515625, 0.04166603088378906, 0.041666507720947266, 0.041666626930236816, 0.041666656732559204, 0.0416666641831398, 0.0416666679084301, 0.0416666716337204, 0.04166668653488159, 0.04166674613952637, 0.04166698455810547, 0.041667938232421875, 0.0416717529296875]
The increments from both data sets are equal.
2 - SST SPREAD. In the annual SST file for 2020, I noticed that the areas of inland water such as lakes and rivers seem larger than they are in reality. Has any 'spread' occurred during the creation of these files that would make values leak out of the real world boundaries of these bodies of water?
3 - SPIKE CHLOR ANOMALY. In the monthly aqua NC files for 2020, I noticed a spike in the chlor_a value for a particular point during the month of February. The spike was approx 98.8. However, the mode for the remainder of the year was only 3.3 approx. I investigated further by analyzing the daily data for this point for February. There was only 1 valid data point - the 16th of February. To verify, I ran the same check for all points adjoining the original point, and they had the same singular high value on the 16th. Has data corruption occurred at this point? The point is just off the coast of Brisbane, Australia. I also noticed that the annual value for this point was listed as 98.8, which is not the average over the course of the year. What type of algorithm is being using to determine which values to show on the annual data sets? Is the scale of 0 to 100 for chlor_a the true chlor value in MG or has some other factor been applied to it?
4 - I am processing many data files as part of my study. Does NASA have a public facing REST API, or similar, that allows me to read directly from the Aqua chlor and SST databases in a more flexible way, rather than having to download and process NC data?