ASDC | PEM-Tropics-A_jValue_AircraftInSitu_DC8_Data

PEM-Tropics Level 2

Entry Title: PEM Tropics A DC-8 Photolysis Frequencies (J-Values)

Entry ID: PEM-Tropics-A_jValue_AircraftInSitu_DC8_Data_1

Field Campaigns

Description

PEM-Tropics-A_jValue_AircraftInSitu_DC8_Data is the photolysis frequencies (j-values) measured along the DC-8 flight during the Pacific Exploratory Mission (PEM) Tropics A suborbital campaign. Data collection for this product is complete.

From 1983-2001, NASA conducted a collection of field campaigns as part of the Global Tropospheric Experiment (GTE). Among those was PEM, which intended to improve the scientific understanding of human influence on tropospheric chemistry. Part of the PEM field campaigns were focused on the tropical Pacific region (PEM-Tropics) which was recognized as a “very large chemical vessel.” The overarching science objective was to assess the anthropogenic impact on tropospheric oxidizing power. A secondary objective was to investigate the impact of atmospheric sulfur chemistry, including oxidation of marine biogenic emission of dimethyl sulfide (DMS) on aerosol loading and radiative effect, which is of critical importance in the assessment of global climate change. The PEM-Tropics mission was conducted in two phases to contrast the influence of biomass burning in the dry season and the “relatively clean” wet season. The first, PEM-Tropics A, was carried out during the end of the dry season (August-September 1996), and the second, PEM-Topics B, was conducted during the wet season (March-April 1999).

To accomplish its objectives, PEM-Tropics enlisted the NASA DC-8 and P-3B aircrafts to carry out longitudinal and latitudinal surveys at various altitudes as well as vertical profile sampling across the Pacific basin. Both aircrafts were equipped with in-situ instruments measuring hydroperoxyl radicals (HOx), ozone (O3), photochemical precursors (including, reactive nitrogen species and non-methane hydrocarbon species), and intermediate products (e.g., hydrogen peroxide (H2O2), formaldehyde (CH2O), and acetic acid (CH3OOH). The P3-B in-situ instrument payload also included a direct measurement of hydroxyl (OH) for both missions, while the OH and hydroperoxyl radical (HO2) measurements were added to DC-8 aircraft for PEM-Tropics B. Taking advantage of its excellent low altitude capability, the P-3B was instrumented with a comprehensive sulfur measurement package and conducted pseudo-Lagragian sampling for evaluating DMS oxidation chemistry, including measurements of DMS, sulfur dioxide (SO2), sulfuric acid (H2SO4), and methylsulfonic acid (MSA) as well as the first airborne measurement of dimethyl sulfoxide (DMSO) during PEM-Tropics B. More importantly, it was the first time that DMS (the source), OH and O3 (primary oxidants), and products (DMSO, MSA, H2SO4, SO2) were measured simultaneously aboard an aircraft in the tropical pacific. These observations, specifically DMSO, presented a substantial challenge to the DMS oxidation kinetics to this day. The DC-8 aircraft was equipped with the Differential Absoprtion Lidar (DIAL) during PEM-Tropics A, and the differential absorption lidars DIAL and LASE during PEM-Tropics B. These lidars provided real-time information for fine tuning the flight tracks to capture sampling opportunities. The lidar data products themselves provide valuable information of vertical profiles of ozone as well as aerosol and water vapor in tropical Pacific Furthermore, both aircrafts were fitted with instruments for aerosol composition and microphysical property measurements. Detailed description related to the motivation, implementation, and instrument payloads are available in the PEM-Tropics A overview paper and the PEM-Tropics B overview paper. Most of the publications based on PEM-Tropics A and B observations are available in the Journal of Geophysical Research special issues: Pacific Exploratory Mission-Tropics A and NASA Global Tropospheric Experiment Pacific Exploratory Mission in the Tropics Phase B: Measurement and Analyses (PEM-Tropics B), while other publications such as Nowak et al. (2001) were published prior to the special issues.

DOI

10.5067/ASDC/SUBORBITAL/PEM-Tropics-A/jValue_AircraftInSitu_DC8_Data_1

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GENERAL DOCUMENTATION

GTE Data Format
GTE Field Missions
PEM Tropics A Participants & Measurements
PEM Tropics A Results
PEM Tropics A Summary

From GCMD Science Keywords:

PHOTOLYSIS RATES > PHOTOCHEMISTRY
DIMETHYL SULFIDE > SULFUR COMPOUNDS
HYDROGEN PEROXIDE > OXYGEN COMPOUNDS
CARBON AND HYDROCARBON COMPOUNDS
NITROUS OXIDE > NITROGEN COMPOUNDS
ATMOSPHERIC WATER VAPOR
HYDROXYL > HYDROGEN COMPOUNDS
NITROGEN DIOXIDE > NITROGEN COMPOUNDS
ATMOSPHERIC CARBON DIOXIDE > CARBON AND HYDROCARBON COMPOUNDS
ATMOSPHERIC NITRIC ACID > NITROGEN COMPOUNDS
ATMOSPHERIC OZONE > OXYGEN COMPOUNDS
ATMOSPHERIC CARBON MONOXIDE > CARBON AND HYDROCARBON COMPOUNDS
FORMALDEHYDE > CARBON AND HYDROCARBON COMPOUNDS

Data Distribution

File Format(s):

GTE

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Spatial Information

Spatial Coverage: (S: -70.33, N: 45.15), (W: -180, E: 180)
Spatial Coverage Type: Horizontal Vertical
Coordinate System: Cartesian
Granule Spatial Representation: Cartesian

Locations

PACIFIC OCEAN CHRISTMAS ISLAND HAWAIIAN ISLANDS FIJI GALAPAGOS ISLANDS NEW ZEALAND WESTERN HEMISPHERE SOUTHERN HEMISPHERE TROPOSPHERE

Temporal Information

Temporal Coverage: 1996-09-04 - 1998-10-08

Platforms

Models

Data Analysis

SPECTRORADIOMETERS

Metadata Dates

Created on 2024-05-02

Last updated on 2024-05-09