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NIM-Dust

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Browse and Order ARM AMF Niamey Dust Observations Data

Niamey Dust Observations

Niamey aerosol are composed of two main components: dust due to the proximity of the Sahara Desert, and soot from local and regional biomass burning. The purpose of this data product is to identify when the local conditions are dominated by the dust component so that the properties of the dust events can be further studied. To identify the dominant presence of dust, a set of criteria were evaluated using observations from the Aerosol Observing System supported by a visibility sensor and an Multi-Filter Rotating Shadowband Radiometer:

  1. Total scattering for green with 10 um cut-off > 200 1/Mm.
  2. Scattering Angstrom exponent (blue-green) with 10 um cut-off < 0.5.
  3. Scattering Angstrom exponent (blue-green) with 1 um cut-off < 1.
  4. Submicron fraction of scattering for green < 0.25.
  5. Submicron fraction of scattering for green < 0.6.
  6. Single scattering albedo for green with 10 um impactor > 0.89.

Periods during which all the conditions 1-4 or conditions 1-3 and 5-6 are met are considered to be dominated by dust. To eliminate momentary data spikes and short-lived events such as gust fronts, we flag only those periods dominated by dust for several consecutive hours as dust events. A more complete description of this dataset is available in the fourth quarter 2008 science metric report http://www.arm.gov/science/metrics.stm>.

Data Description

Data are reported n ASCII format as hourly averages. A summary file containing daily averages is also provided.

The files contain 78 columns of data as follows:
Fieldname		units			longname/description
---------------------   ----------------------  ------------------------------------------------------------
year			yyyy			year
month			mm			month
day			dd			day of month
Hh			hh			hour of day UTC
jday			decimal year		day of year (Jan 1 = 1)
dust event 		unitless 		dust event flag (0 = not a dust event; 1 = dust event)
Bsp_R_1um		1/Mm			total scattering coefficient (dry), red, 1 um cut-off
Bsp_G_1um		1/Mm			total scattering coefficient (dry), green, 1 um cut-off
Bsp_B_1um		1/Mm			total scattering coefficient (dry), blue, 1 um cut-off
Bsp_R_10um		1/Mm			total scattering coefficient (dry), red, 10 um cut-off
Bsp_G_10um		1/Mm			total scattering coefficient (dry), green, 10 um cut-off
Bsp_B_10um		1/Mm			total scattering coefficient (dry), blue, 10 um cut-off
Bbsp_R_1um		1/Mm			backscattering coefficient (dry), red, 1 um cut-off
Bbsp_G_1um		1/Mm			backscattering coefficient (dry), green, 1 um cut-off
Bbsp_B_1um		1/Mm			backscattering coefficient (dry), blue, 1 um cut-off
Bbsp_R_10um		1/Mm			backscattering coefficient (dry), red, 10 um cut-off
Bbsp_G_10um		1/Mm			backscattering coefficient (dry), green, 10 um cut-off
Bbsp_B_10um		1/Mm			backscattering coefficient (dry), blue, 10 um cut-off
Bap_R_1um		1/Mm			absorption coefficient (dry), red, 1 um cut-off
Bap_G_1um		1/Mm			absorption coefficient (dry), green, 1 um cut-off
Bap_B_1um		1/Mm			absorption coefficient (dry), blue, 1 um cut-off
Bap_R_10um		1/Mm			absorption coefficient (dry), red, 10 um cut-off
Bap_G_10um		1/Mm			absorption coefficient (dry), green, 10 um cut-off
Bap_B_10um		1/Mm			absorption coefficient (dry), blue, 10 um cut-off
SSA_R_1um		unitless		single-scattering albedo, red, 1 um cut-off
SSA_G_1um		unitless		single-scattering albedo, green, 1 um cut-off
SSA_B_1um		unitless		single-scattering albedo, blue, 1 um cut-off
SSA_R_10um		unitless		single-scattering albedo, red, 10 um cut-off
SSA_G_10um		unitless		single-scattering albedo, green, 10 um cut-off
SSA_B_10um		unitless		single-scattering albedo, blue, 10 um cut-off
bsf_R_1um		unitless		backscatter fraction , red, 1 um cut-off
bsf_G_1um		unitless		backscatter fraction , green, 1 um cut-off
bsf_B_1um		unitless		backscatter fraction , blue, 1 um cut-off
bsf_R_10um		unitless		backscatter fraction , red, 10 um cut-off
bsf_G_10um		unitless		backscatter fraction , green, 10 um cut-off
bsf_B_10um		unitless		backscatter fraction , blue, 10 um cut-off
g_R_1um			unitless		asymmetry parameter, red, 1 um cut-off
g_G_1um			unitless		asymmetry parameter, green, 1 um cut-off
g_B_1um			unitless		asymmetry parameter, blue, 1 um cut-off
g_R_10um		unitless		asymmetry parameter, red, 10 um cut-off
g_G_10um		unitless		asymmetry parameter, green, 10 um cut-off
g_B_10um		unitless		asymmetry parameter, blue, 10 um cut-off
Ang_Bs_BG_1um		unitless		Angstrom exponent for scattering, blue-green,1 um cut-off
Ang_Bs_BR_1um		unitless		Angstrom exponent for scattering, blue-red,1 um cut-off
Ang_Bs_GR_1um		unitless		Angstrom exponent for scattering, green-red,1 um cut-off
Ang_Bs_BG_10um		unitless		Angstrom exponent for scattering, blue-green,10 um cut-off
Ang_Bs_BR_10um		unitless		Angstrom exponent for scattering, blue-red,10 um cut-off
Ang_Bs_GR_10um		unitless		Angstrom exponent for scattering, green-red,10 um cut-off
Ang_Ba_BG_1um		unitless		Angstrom exponent for absorption, blue-green,1 um cut-off
Ang_Ba_BR_1um		unitless		Angstrom exponent for absorption, blue-red,1 um cut-off
Ang_Ba_GR_1um		unitless		Angstrom exponent for absorption, green-red,1 um cut-off
Ang_Ba_BG_10um		unitless		Angstrom exponent for absorption, blue-green,10 um cut-off
Ang_Ba_BR_10um		unitless		Angstrom exponent for absorption, blue-red,10 um cut-off
Ang_Ba_GR_10um		unitless		Angstrom exponent for absorption, green-red,10 um cut-off
subfrac_Bs_R		unitless		submicron fraction for scattering, red
subfrac_Bs_G		unitless		submicron fraction for scattering, green
subfrac_Bs_B		unitless		submicron fraction for scattering, blue
subfrac_Ba_R		unitless		submicron fraction for absorption, red
subfrac_Ba_G		unitless		submicron fraction for absorption, green
subfrac_Ba_B		unitless		submicron fraction for absorption, blue
CN_frac_ss_p5		unitless		Ratio of CCN at 0.5% supersaturation to total CPC counts
CN_frac_ss_p7		unitless		Ratio of CCN at 0.7% supersaturation to total CPC counts
CN_frac_ss_p9		unitless		Ratio of CCN at 0.9% supersaturation to total CPC counts
CN_frac_ss_1p2		unitless		Ratio of CCN at 1.2% supersaturation to total CPC counts
aod_415nm		unitless		MFRSR aod 415 nm, corrected for forward scattering
aod_500nm		unitless		MFRSR aod 500 nm, corrected for forward scattering
aod_615nm		unitless		MFRSR aod 615 nm, corrected for forward scattering
aod_673nm		unitless		MFRSR aod 673 nm, corrected for forward scattering
aod_870nm		unitless		MFRSR aod 870 nm, corrected for forward scattering
Ang_aod_500_870		unitless		MFRSR angstrom exponent from 500nm and 870nm aod
twr_vis_10min		km			visibility from Vaisala sensor on met tower
wind_spd		m/s			vector avg wind speed from tower
wind_dir		CW degrees from north	vector avg wind direction from tower, measured clockwise from N=0.
wind_N			m/s			component of windspeed from the north
wind_E			m/s			component of windspeed from the east
T_amb			C 			Ambient temperature
RH_amb			%			Ambient relative humidty
atmos_pres  		hPa			atmospheric pressure

Contact Information

Connor Flynn
connor.flynn@pnl.gov
509-375-2041