MCD15A3H

[lixiyu1166]

I am conducting experimental research using the MCD15A3H dataset to study winter wheat in the plain areas of China, but I have encountered an issue. Under normal circumstances, the LAI value of winter wheat from March to May should be between 3 and 8. But in the data I have obtained, many of the data have anomalies, that is, the LAI data of winter wheat sampling points are mostly less than 3. I have checked my data acquisition method and there is no problem. May I ask why there is a situation where the LAI value is lower than the normal value?

[LP DAAC - lien]

Hello,
Could you give me some specific examples. Like the H/V Lat/long range and date, then we could look at specific examples. Also, did you get a chance to look at the QC bits to see if those would indicate what may be wrong with the pixels?
Thanks,
Brett

[lixiyu1166]

LP DAAC - lien wrote:
> Hello,
> Could you give me some specific examples. Like the H/V Lat/long range and
> date, then we could look at specific examples. Also, did you get a chance
> to look at the QC bits to see if those would indicate what may be wrong
> with the pixels?
> Thanks,
> Brett
Hi, Brett! Thanks for you attention! The H/V is h27v05, and I obtained it based on GEE. For example, the lon/lat of a sample is 116.992617/35.452. This is a winter wheat sample. But all data I obtained from 2018/12/01 to 2019/06/31 are less than 1.5. Could you please help me?

[LP DAAC - lien]

Hi,

LAI_Charts_China.PNG (232.97 KiB) Not viewed yet

I processed February 1 through June 30 from 2012-2023 in our AppEEARS tool and they seem consistent, so at least there is no dramatic spike or drop from year to year, but the highest value I see is 2.3. The vast majority are between 0.5 and 1.5, so the issue is should they be higher then this. I will check into this with the science team and let you know what their take is. Please see the image attached for charts of this process.
Thanks,
Brett

[lixiyu1166]

LP DAAC - lien wrote:
> Hi,
> LAI_Charts_China.PNGI processed February 1 through June 30 from 2012-2023
> in our AppEEARS tool and they seem consistent, so at least there is no
> dramatic spike or drop from year to year, but the highest value I see is
> 2.3. The vast majority are between 0.5 and 1.5, so the issue is should
> they be higher then this. I will check into this with the science team
> and let you know what their take is. Please see the image attached for
> charts of this process.
> Thanks,
> Brett



Thank you very much! The issue is indeed this. This sampling point is a winter wheat planting site. According to previous experiments and research, the LAI of winter wheat from March to May should be between 3 and 8. We hope you can pay close attention to it. The same points also include 114.5193048/36.17419807(lon/lat), 112.1314256/32.19404648, 109.1326177/34.62616704, 115.296/33.6158, etc. I am looking forward to your future research results!
Thanks,
Li Xiyu

[LP DAAC - lien]

Hi Li Xiyu,
Can you tell me what Lai product you are comparing the MCD15s to?
Thanks,
Brett

[lixiyu1166]

LP DAAC - lien wrote:
> Hi Li Xiyu,
> Can you tell me what Lai product you are comparing the MCD15s to?
> Thanks,
> Brett
Hi Brett，
I compared the product with field observation data before. And I currently plan to use other satellite products. I will contact you after we get the results.
Thanks,
Li Xiyu