# MLS_L2_HNO3

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `MLS_L2_HNO3` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
datetime | double | {time} | [seconds since 2000-01-01] | time of the measurement
longitude | double | {time} | [degree_east] | tangent longitude
latitude | double | {time} | [degree_north] | tangent latitude
pressure | double | {vertical} | [hPa] | pressure per profile level
HNO3_volume_mixing_ratio | double | {time, vertical} | [ppv] | HNO3 volume mixing ratio
HNO3_volume_mixing_ratio_uncertainty | double | {time, vertical} | [ppv] | uncertainty of the HNO3 volume mixing ratio
HNO3_volume_mixing_ratio_validity | int32 | {time, vertical} |  | quality flag for the HNO3 volume mixing ratio
index | int32 | {time} |  | zero-based index of the sample within the source product

## Mapping description

Bits 4 to 9 and 11 to 14 in the quality flag denote a specific error condition while bits 0 to 2 denote the severity (bit 0 error, bit 1 warning, bit 2 comment).

Bits 4 to 9 denote the MLS status (bit 4 HICLOUD, bit 5 LOWCLOUD, bit 6 NO_APRIORI_T, bit 7 NUM_ERROR, bit 8 TOO_FEW_RAD, bit 9 GLOB_FAILURE).

Bits 11 to 14 denote specific checks as specified in the EOS MLS data quality document (the pressure range, quality and convergence thresholds come from table 1.1.1 in issue 4.x-4.0 of that document): Bit 11 denotes pressure out of range, bit 12 denotes quality below threshold, bit 13 denotes convergence above threshold and bit 14 denotes a negative precision. Also, if any of the bits 11 to 14 is set, bit 0 is automatically set.

Bits 15 and 16 denote the results of checks that are only performed for the HNO3 product. Bit 15 is set if the pressure is at most 68 hPa and the quality flag is not zero. Bit 16 is set if either the pressure is at least 316 hPa and the volume mixing ratio is less than -2.0 or the pressure is between 68 hPa and 215 hPa and the volume mixing ratio is less than -1.2. Again, if any of the bits 15 and 16 is set, bit 0 is automatically set.

The table below details where and how each variable was retrieved from the input product.

field name | mapping description
--- | ---
datetime | path | /HDFEOS/SWATHS/HNO3/Geolocation_Fields/Time[]
description | the time converted from TAI93 to seconds since 2000-01-01T00:00:00
longitude | path | /HDFEOS/SWATHS/HNO3/Geolocation_Fields/Longitude[]
latitude | path | /HDFEOS/SWATHS/HNO3/Geolocation_Fields/Latitude[]
pressure | path | /HDFEOS/SWATHS/HNO3/Geolocation_Fields/Pressure[]
HNO3_volume_mixing_ratio | path | /HDFEOS/SWATHS/HNO3/Data_Fields/L2gpValue[]
HNO3_volume_mixing_ratio_uncertainty | path | /HDFEOS/SWATHS/HNO3/Data_Fields/L2gpPrecision[]
HNO3_volume_mixing_ratio_validity | path | /HDFEOS/SWATHS/HNO3/Data_Fields/Status[], /HDFEOS/SWATHS/HNO3/Data_Fields/Quality[], /HDFEOS/SWATHS/HNO3/Data_Fields/Convergence[], /HDFEOS/SWATHS/HNO3/Data_Fields/L2gpPrecision[], /HDFEOS/SWATHS/HNO3/Geolocation_Fields/Pressure[]
description | see generic mapping description