Measuring aerosols caused by biomass burning

Author:贾斯汀·费舍尔

From June to October, the burning of agricultural fields in southern Africa creates smoke that blows west across the south-eastern Atlantic Ocean and reaches Brazil,more than 4,500 miles (7,242 kilometres)离开。使用微脉冲激光雷达（MPL）和其他仪器，由美国能源部运营的大气辐射测量（ARM）用户设施的研究人员，collected data for 16 monthsto help understand how these airborne particles impact the climate.

Better data needed in climate models

Biomass burning (BB) produces aerosols that enter the atmosphere. A significant amount of this particulate matter consists of black carbon and other carbonaceous aerosols that absorb light, warming the atmosphere; however, if the underlying surface is a dark ocean, the particles reflect light, cooling the atmosphere.Scientists need accurate measurementsof each type of aerosol in the layers of the atmosphere tostudy the movement and long-term consequences of the smoke。

Currently, the vertical extent of the BB aerosol layers transported far from the sources is poorly represented in global climate models. To help improve the models, ARM deployed one of its mobile atmospheric observatories for the Layered Atlantic Smoke Interactions with Clouds (LASIC) campaign from June 2016 to October 2017 on Ascension Island,about 1,000 mi. (1,609 km)off the west coast of Africa. From this unique location, researchers recorded measurements from numerous instruments to compile a comprehensive dataset representing two BB seasons.

Micro Pulse LiDAR used in LASIC research

The ARM Mobile Facility on Ascension Island

ARM launched the LASIC campaign specifically to gather data on how smoke properties (i.e., ability to absorb shortwave radiation) change after long-range atmospheric transport, as well as the smoke’s effect on clouds. While aerosol surface measurements were available from multiple instruments, to study the vertical structure and the monthly and seasonal variations of the BB aerosol layers transported to this remote island, it was important to include profiling instrumentation.

“One of the critical MPL capabilities for LASIC is its dual-polarisation capability, which allows discrimination of smoke, dust and sea salt aerosol layers above Ascension Island,”said Paytsar Muradyan, Argonne National Laboratory researcher.”同时,手臂移动设施经常deployed in remote locations around the world, and MPL is capable of providing unattended continuous observations of clouds and aerosols.”

Extinction profiles from one day of MPL observations (2018-08-15) show a sinking smoke layer over 21 hours from approximately 2.8 km at hour 00 to approximately 1.8 km at hour 21.

在整个激光场运动中，收集了由大气颗粒的反向散射信号曲线组成的原始MPL测量值。ARM数据中心（ADC）摄入了每小时的原始数据以及MPL校正，气候和预测（CF）标准化NETCDF文件在ADC上存档以帮助验证结果。

The analysis of the monthly variations of the retrieved extinction profiles provides a first look into the ‘evolution’of the pre-BB and BB season aerosol vertical structure and elevated smoke layer depths over Ascension Island. High amounts of aerosols that can affect the Earth’s energy balance and cloud properties are common in the marine boundary layer during the southern African burning season (June-October).

The MPL data shows thesmoke layer is present mostly above boundary layer云between 1.5 to 3 kmat the beginning of the burning season in July and9月延伸到4公里。BB烟层的发生与在表面观察到的黑色峰浓度（> 1,000纳米图/立方米）一致，这表明这些气溶胶非常吸收，因为背部轨迹表明它们起源于相同的大陆BB区域。

“The data collected during LASIC improve our current understanding of aerosol vertical distribution and their radiative impact,”says Paquita Zuidema, principal investigator of the LASIC campaign.“This will ultimately lead to improved accuracy of long-term climate forecasts and help us develop sustainable solutions to energy and environmental challenges.”

Elevating atmospheric monitoring

Smoke envelopes the first ARM Mobile Facility during a hazy day on Ascension Island, which is located in the South Atlantic Ocean.

MPL instruments help scientists, meteorologists and air quality professionals monitor aerosols to better understand the structure of our atmosphere. MPL’s long-range capabilities and high-quality signal increase the efficiency and accuracy of the data capture process for improved atmospheric monitoring. Originally designed by Sigma Space for NASA, now part of Hexagon, MPL uses eye-safe lasers, precision photon counting, and built-in data analysis to deliver the best signal-to-noise ratio, providing the most reliable information in this category.