Hi,
I am analyzing the HNO3 mixing ratio from CALIPSO Lidar Level2 Polar Stratospheric Cloud Data Product and I am having negative values by directly reading the HDF files that are provided. The negative values vary and are of the order of the positive ones, just negative.
I have checked the description: it shouldn't be any and it is not the fill value.
https://www-calipso.larc.nasa.gov/resources/calipso_users_guide/data_summaries/psc/cal_lid_l2_pscmask_v2-00_desc.php#HNO3_Mixing_Ratio
I have checked them in some years (2020/03/01, 2017/03/01, 2010/03/01) and they are not rare.
I have worked with temperature and water data from this same product and I haven't had any negative values. How should I treat them? Thank you very much.
CALIPSO Level 2 Polar Stratospheric Cloud HNO3 Data Product
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ASDC - cheyenne.e.land
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Re: CALIPSO Level 2 Polar Stratospheric Cloud HNO3 Data Product
Hello,
Thank you for your interest in CALIPSO data.
We reached out to a member of the CALIPSO Science team and they stated that the negative HNO3 values do occur in the Aura MLS data due to noise in the measurements, especially in the SH winter when values are close to zero. These values are not filtered out since they are NOT considered “bad” by the MLS team. This is an example of where the User’s Guide lists the “valid” range of the data as the expected physically possible range. The V3 PSC product, will include negative values in the range. The CALIPSO team suggested that you access the Aura MLS data directly from the MLS project archive if you are are using it for anything other than PSC studies. The negative values are discussed in the MLS user’s guide.
Thanks,
ASDC
Thank you for your interest in CALIPSO data.
We reached out to a member of the CALIPSO Science team and they stated that the negative HNO3 values do occur in the Aura MLS data due to noise in the measurements, especially in the SH winter when values are close to zero. These values are not filtered out since they are NOT considered “bad” by the MLS team. This is an example of where the User’s Guide lists the “valid” range of the data as the expected physically possible range. The V3 PSC product, will include negative values in the range. The CALIPSO team suggested that you access the Aura MLS data directly from the MLS project archive if you are are using it for anything other than PSC studies. The negative values are discussed in the MLS user’s guide.
Thanks,
ASDC