MOD16A2 Unit Conversion

Use this Forum to find information on, or ask a question about, NASA Earth Science data.
subhadip_007
Posts: 1
Joined: Thu Dec 30, 2021 9:34 am America/New_York
Answers: 0

MOD16A2 Unit Conversion

by subhadip_007 » Thu Dec 30, 2021 9:45 am America/New_York

I need ET in m/8d or mm/8d. How to convert MOD16A2 kg/m²/8day to one of my units? Please help me with this. Or any other dataset I can use with my unit.

Filters:

LP DAAC - lien
User Services
User Services
Posts: 185
Joined: Thu Jun 25, 2020 9:51 am America/New_York
Answers: 1
Been thanked: 6 times

Re: MOD16A2 Unit Conversion

by LP DAAC - lien » Fri Jan 14, 2022 8:53 am America/New_York

Hi,
Sorry for the delay, we wanted to confirm with the developer of the product.
"The kg/m2/8day units are equivalent to mm/8day. Therefore, you just need to apply the 0.1 scale factor to get ET in the desired mm/8day units as noted below. As a check, the typical ET rate over a humid temperate grassland in summer would be ~1-4 mm/day."
Thanks,
Brett

valeria_22
Posts: 1
Joined: Mon Oct 31, 2022 10:30 am America/New_York
Answers: 0

Re: MOD16A2 Unit Conversion

by valeria_22 » Mon Oct 31, 2022 10:33 am America/New_York

Hello
I need ET in mm/day. how to convert MOD16A2 kg/m²/8 day to one of my units?

LP DAAC - dgolon
User Services
User Services
Posts: 317
Joined: Mon Sep 30, 2019 10:00 am America/New_York
Answers: 0
Has thanked: 24 times
Been thanked: 3 times
Contact:

Re: MOD16A2 Unit Conversion

by LP DAAC - dgolon » Tue Nov 01, 2022 10:05 am America/New_York

Hi @valeria_22 ,

Above we listed the answer for mm/8 day, so you would just need to divide by 8 to get mm/day. However, if you are interested in ~daily data you might be interested in ECOSTRESS ET data which can be found here: https://lpdaac.usgs.gov/product_search/?query=ecostress&keyword=Evapotranspiration+%28ET%29&status=Operational&view=cards&sort=title
Subscribe to the LP DAAC listserv by sending a blank email to lpdaac-join@lists.nasa.gov.

Sign up for the Landsat listserv to receive the most up to date information about Landsat data: https://public.govdelivery.com/accounts/USDOIGS/subscriber/new#tab1.

linzeearth
Posts: 2
Joined: Wed Feb 15, 2023 9:18 pm America/New_York
Answers: 0

Re: MOD16A2 Unit Conversion

by linzeearth » Wed Feb 15, 2023 9:19 pm America/New_York

Hi@LP DAAC - dgolon,

I am so confuse about the unit mm/8 day, does it mean a average number of 8 day?
and how can i calculate the evaporation over a year with that unit?

thank you

LP DAAC - dgolon wrote:
> Hi @valeria_22 ,
>
> Above we listed the answer for mm/8 day, so you would just need to divide
> by 8 to get mm/day. However, if you are interested in ~daily data you might
> be interested in ECOSTRESS ET data which can be found here:
> https://lpdaac.usgs.gov/product_search/?query=ecostress&keyword=Evapotranspiration+%28ET%29&status=Operational&view=cards&sort=title
Last edited by linzeearth on Wed Feb 15, 2023 9:23 pm America/New_York, edited 1 time in total.

LP DAAC - dgolon
User Services
User Services
Posts: 317
Joined: Mon Sep 30, 2019 10:00 am America/New_York
Answers: 0
Has thanked: 24 times
Been thanked: 3 times
Contact:

Re: MOD16A2 Unit Conversion

by LP DAAC - dgolon » Thu Feb 23, 2023 10:46 am America/New_York

Hi @linzeearth The pixel values for the two Evapotranspiration layers (ET and PET) are the sum of all eight days within the composite period and the pixel values for the two Latent Heat layers (LE and PLE) are the average of all eight days within the composite period. Note that the last acquisition period of each year is a 5 or 6-day composite period, depending on the year.

You could average the data out to yearly but you will have some error you would need to identify. Instead, we recommend using the yearly product: https://doi.org/10.5067/MODIS/MOD16A3GF.061 You might also be interested in the Daily MODIS ET SSEBop Evapotranspiration data product. More information on that can be found here: https://earlywarning.usgs.gov/ssebop/modis/daily Thank you
Subscribe to the LP DAAC listserv by sending a blank email to lpdaac-join@lists.nasa.gov.

Sign up for the Landsat listserv to receive the most up to date information about Landsat data: https://public.govdelivery.com/accounts/USDOIGS/subscriber/new#tab1.

schsu
Posts: 1
Joined: Fri Aug 18, 2023 5:47 am America/New_York
Answers: 0

Re: MOD16A2 Unit Conversion

by schsu » Fri Aug 18, 2023 6:19 am America/New_York

Hi,

I have downloaded the 8-day evapotranspiration data (MOD16A2GF.061_ET_500m_doy2005XXX_aid0001.tif) from the online tool AppEEARS (https://appeears.earthdatacloud.nasa.gov). The tif files were generated according to the shapefile I uploaded.

Based on the previous reply and the user guide, the raw values in the data (integer) should be multiplied by the scale factor 0.1 to be the real value. However, I found in the tif files the values are already not integers. Also, the statistical analysis presented in the AppEEARS download section also uses (kg/m2/8day) as unit for ET_500m.

Therefore, I am wondering if the multiplication of the scale factor is already processed during the generation of tif files from AppEEARS. In other words, is it true that the MOD16A2 products downloaded from AppEEARS do not need to consider the scale factor?

Thank you in advance for your reply.

LP DAAC - lien
User Services
User Services
Posts: 185
Joined: Thu Jun 25, 2020 9:51 am America/New_York
Answers: 1
Been thanked: 6 times

Re: MOD16A2 Unit Conversion

by LP DAAC - lien » Mon Aug 21, 2023 11:32 am America/New_York

Hello,
The values in the .csv file are already scaled. However, the geotiff files are not supposed to be scaled.
Thanks,
Brett

fredhensley
Posts: 2
Joined: Wed Jan 03, 2024 5:49 am America/New_York
Answers: 0

Re: MOD16A2 Unit Conversion

by fredhensley » Wed Jan 03, 2024 5:53 am America/New_York

Hi all,
Can you advise with converting to imperial units?
I still do it manually: https://oneconvert.com/unit-converters/length-converter/mm-to-inches
Thanks in advance.

LP DAAC - lien
User Services
User Services
Posts: 185
Joined: Thu Jun 25, 2020 9:51 am America/New_York
Answers: 1
Been thanked: 6 times

Re: MOD16A2 Unit Conversion

by LP DAAC - lien » Wed Jan 03, 2024 9:29 am America/New_York

Hello,
We typically work in metric but I'll see if anyone on our staff knows an easy way to convert. In the meantime, if anyone in the science community works in imperial we'll leave it open for you to share what you do. It does appear that the .csv file allows formulas to be entered for specific columns, so there should be a way.

Post Reply