# SCIAMACHY_L2_LIMB_UV1_NO2

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `SCIAMACHY_L2_LIMB_UV1_NO2` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
datetime_start | double | {time} | [seconds since 2000-01-01] | measurement start time for each profile
datetime_length | double | {time} | [s] | measurement integration time
orbit_index | int32 |  |  | absolute orbit number
altitude_bounds | double | {time, vertical, 2} | [km] | altitude bounds for each profile point
pressure_bounds | double | {time, vertical, 2} | [hPa] | pressure bounds for each profile point
latitude | double | {time} | [degree_north] | tangent latitude of the vertically mid profile point
longitude | double | {time} | [degree_east] | tangent longitude of the vertically mid profile point
solar_zenith_angle | double | {time} | [degree] | solar zenith angle at top of atmosphere for the middle most profile point
viewing_zenith_angle | double | {time} | [degree] | line of sight zenith angle at top of atmosphere for the middle most profile point
relative_azimuth_angle | double | {time} | [degree] | relative azimuth angle at top of atmosphere for the middle most profile point
temperature | double | {time, vertical} | [K] | temperature for each profile point
NO2_volume_mixing_ratio | double | {time, vertical} | [ppv] | NO2 volume mixing ratio
NO2_volume_mixing_ratio_uncertainty | double | {time, vertical} | [ppv] | error on the NO2 volume mixing ratio
NO2_volume_mixing_ratio_avk | double | {time, vertical, vertical} | [] | averaging kernel on the NO2 volume mixing ratio
NO2_number_density | double | {time, vertical} | [molec/cm^3] | NO2 number density
NO2_number_density_uncertainty | double | {time, vertical} | [molec/cm^3] | error on the NO2 number density
NO2_number_density_apriori | double | {time, vertical} | [molec/cm^3] | a priori NO2 number density profile
NO2_number_density_avk | double | {time, vertical, vertical} | [(molec/cm^3)/(molec/cm^3)] | averaging kernel on the NO2 number density
index | int32 | {time} |  | zero-based index of the sample within the source product

## Ingestion options

The table below lists the available ingestion options for `SCIAMACHY_L2` products.

option name | legal values | description
--- | --- | ---
dataset | nad_uv0_o3, nad_uv1_no2, nad_uv3_bro, nad_uv4_h2co, nad_uv5_so2, nad_uv6_oclo, nad_uv7_so2, nad_uv8_h2o, nad_uv9_chocho, nad_ir0_h2o, nad_ir1_ch4, nad_ir2_n2o, nad_ir3_co, nad_ir4_co2, lim_uv0_o3, lim_uv1_no2, lim_uv3_bro, clouds_aerosol | the dataset of the L2 product to ingest; each dataset is a combination of nadir/limb choice, retrieval window, and main quantity; option values are ‘nad_uv0_o3’ (default), ‘nad_uv1_no2’, ‘nad_uv3_bro’, ‘nad_uv4_h2co’, ‘nad_uv5_so2’, ‘nad_uv6_oclo’, ‘nad_uv7_so2’, ‘nad_uv8_h2o’, ‘nad_uv9_chocho’, ‘nad_ir0_h2o’, ‘nad_ir1_ch4’, ‘nad_ir2_n2o’, ‘nad_ir3_co’, ‘nad_ir4_co2’, ‘lim_uv0_o3’, ‘lim_uv1_no2’, ‘lim_uv3_bro’, ‘clouds_aerosol’

This definition is only applicable when: dataset=lim_uv1_no2

## Mapping description

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

field name | mapping description
--- | ---
datetime_start | path | /geolocation_limb[]/dsr_time
description | records in geolocation_limb do not have a one-to-one mapping with records in the limb/occultation measurement datasets; HARP uses a single measurement time and tangent location per profile which is taken from the middlemost measurement used for the retrieval (i.e. index = (n_meas - 1) / 2); the geolocation record for this measurement is retrieved by matching the measurement time measurement_grid[(n_meas - 1) / 2].dsr_time with the geolocation record time geolocation_limb[]/dsr_time
datetime_length | path | /lim_uv1_no2[]/integr_time
orbit_index | path | /mph/abs_orbit
altitude_bounds | path | /lim_uv1_no2[]/tangent_height[]
description | the tangent heights are the lower bound altitudes; for the top of the highest layer a TOA value of 100km is used
pressure_bounds | path | /lim_uv1_no2[]/tangent_pressure[]
description | the tangent pressures are the lower bound pressures; for the top of the highest layer a pressure value of 3.2e-4 hPa is used
latitude | path | /geolocation_limb[]/tangent_coord[1]/latitude
description | records in geolocation_limb do not have a one-to-one mapping with records in the limb/occultation measurement datasets; HARP uses a single measurement time and tangent location per profile which is taken from the middlemost measurement used for the retrieval (i.e. index = (n_meas - 1) / 2); the geolocation record for this measurement is retrieved by matching the measurement time measurement_grid[(n_meas - 1) / 2].dsr_time with the geolocation record time geolocation_limb[]/dsr_time
longitude | path | /geolocation_limb[]/tangent_coord[1]/longitude
description | records in geolocation_limb do not have a one-to-one mapping with records in the limb/occultation measurement datasets; HARP uses a single measurement time and tangent location per profile which is taken from the middlemost measurement used for the retrieval (i.e. index = (n_meas - 1) / 2); the geolocation record for this measurement is retrieved by matching the measurement time measurement_grid[(n_meas - 1) / 2].dsr_time with the geolocation record time geolocation_limb[]/dsr_time
solar_zenith_angle | path | /geolocation_limb[]/sol_zen_angle_toa[1]
description | records in geolocation_limb do not have a one-to-one mapping with records in the limb/occultation measurement datasets; HARP uses a single measurement time and tangent location per profile which is taken from the middlemost measurement used for the retrieval (i.e. index = (n_meas - 1) / 2); the geolocation record for this measurement is retrieved by matching the measurement time measurement_grid[(n_meas - 1) / 2].dsr_time with the geolocation record time geolocation_limb[]/dsr_time
viewing_zenith_angle | path | /geolocation_limb[]/los_zen_angle_toa[1]
description | records in geolocation_limb do not have a one-to-one mapping with records in the limb/occultation measurement datasets; HARP uses a single measurement time and tangent location per profile which is taken from the middlemost measurement used for the retrieval (i.e. index = (n_meas - 1) / 2); the geolocation record for this measurement is retrieved by matching the measurement time measurement_grid[(n_meas - 1) / 2].dsr_time with the geolocation record time geolocation_limb[]/dsr_time
relative_azimuth_angle | path | /geolocation_limb[]/rel_azi_angle_toa[1]
description | records in geolocation_limb do not have a one-to-one mapping with records in the limb/occultation measurement datasets; HARP uses a single measurement time and tangent location per profile which is taken from the middlemost measurement used for the retrieval (i.e. index = (n_meas - 1) / 2); the geolocation record for this measurement is retrieved by matching the measurement time measurement_grid[(n_meas - 1) / 2].dsr_time with the geolocation record time geolocation_limb[]/dsr_time
temperature | path | /lim_uv1_no2[]/tangent_temp[]
NO2_volume_mixing_ratio | path | /lim_uv1_no2[]/main_species[,0]/tang_vmr
NO2_volume_mixing_ratio_uncertainty | path | /lim_uv1_no2[]/main_species[,0]/err_tang_vmr, /lim_uv1_no2[]/main_species[,0]/tang_vmr
description | relative error is converted to absolute error by multiplying with measured value
NO2_volume_mixing_ratio_avk | available | optional
condition | additional diagnostics vector in limb DSR is long enough to contain number density and AKM information
path | /lim_uv1_no2[]/main_species[,0]/add_diag[0..n]
description | the AVK for partial columns as given in the add_diag vector at position 2+stvec+2*n1*num_altitudes+2*num_altitudes is converted to volume mixing ratio units by multiplying each element with conv_mix_i/conv_mix_j, where conv_mix is found in add_diag at position 2+stvec+2*n1*num_altitudes; the vertical axis of the AVK are reversed
NO2_number_density | available | optional
condition | additional diagnostics vector in limb DSR is long enough to contain number density and AKM information
path | /lim_uv1_no2[]/main_species[,0]/add_diag[0..n]
NO2_number_density_uncertainty | available | optional
condition | additional diagnostics vector in limb DSR is long enough to contain number density and AKM information
path | /lim_uv1_no2[]/main_species[,0]/err_tang_vmr, /lim_uv1_no2[]/main_species[,0]/add_diag[0..n]
description | relative error is converted to absolute error by multiplying with measured value
NO2_number_density_apriori | available | optional
condition | additional diagnostics vector in limb DSR is long enough to contain number density and AKM information
path | /lim_uv1_no2[]/main_species[,0]/add_diag[0..n]
NO2_number_density_avk | available | optional
condition | additional diagnostics vector in limb DSR is long enough to contain number density and AKM information
path | /lim_uv1_no2[]/main_species[,0]/add_diag[0..n]
description | the AVK for partial columns as given in the add_diag vector at position 2+stvec+2*n1*num_altitudes+2*num_altitudes is converted to number density units by multiplying each element with conv_nd_i/conv_nd_j, where conv_nd is found in add_diag at position 2+stvec+2*n1*num_altitudes+num_altitudes; the vertical axis of the AVK are reversed