AERONET—AFederatedInstrumentNetworkandDataArchiveforAerosolCharacterization资源-CSDN文库

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### AERONET—联邦仪器网络与气溶胶特性数据归档 #### 概述 AERONET（AErosol RObotic NETwork）是由美国国家航空航天局（NASA）发起的一个远程感应气溶胶监测网络，旨在支持NASA、法国国家太空研究中心（CNES）以及日本宇宙航空研究开发机构（NASDA）的地球卫星系统。该网络通过国际合作得到扩展，旨在提高全球范围内对大气气溶胶特性的监测能力。 #### 运行原理与特点 AERONET的核心在于使用了天气耐受型自动太阳与天空扫描光谱辐射计，这些设备能够频繁地测量大气中的气溶胶光学性质以及可降水量。通过地球同步卫星GOES和METEOSAT的数据收集系统，可以实现近实时的数据传输与接收，覆盖大约75%的地球表面。随着日本地球同步气象卫星（GMS）的加入，预计在1998年这一覆盖率将提升至90%。 #### 数据处理与分析 NASA开发了一套基于UNIX系统的近实时数据处理、显示与分析系统，该系统提供了互联网接入新兴的全球数据库的功能。用户可以通过项目主页获取相关信息：[http://spamer.gsfc.nasa.gov](http://spamer.gsfc.nasa.gov)。开放访问数据库的理念、集中式数据处理以及用户友好的图形界面促进了国际间合作的增长，并为地面气溶胶监测设定了标准化测量方法。 #### 监测系统的操作与理念 AERONET的运行和理念主要围绕以下几个方面： 1. **监测系统的设计**：AERONET的设计考虑到了远程站点的部署需求，确保即使在恶劣的气候条件下也能持续进行高质量的气溶胶监测。 2. **自动化数据采集与传输**：利用地球同步卫星的数据收集系统实现了数据的快速传输，使得近实时的数据处理成为可能。 3. **数据分析与处理**：NASA开发的基于UNIX系统的处理软件确保了数据的快速分析和结果的及时发布，为用户提供了一个高效的数据访问平台。 4. **开放访问原则**：AERONET遵循开放访问的原则，允许全球科学家和研究人员通过互联网访问其数据库，这极大地促进了科学研究的共享与发展。 #### 测量精度与准确性 AERONET使用的自动太阳与天空扫描光谱辐射计具有较高的精度和准确性。这些设备能够在不同的天气条件下准确测量气溶胶的光学特性，包括散射系数、吸收系数等关键参数，从而确保了数据的质量。 #### 处理系统简介 AERONET的数据处理系统由NASA开发，采用了UNIX操作系统作为基础平台。该系统能够实现数据的自动接收、处理和分析，并提供了一系列工具帮助用户进行数据查询、可视化以及进一步的研究工作。此外，系统还具备强大的数据管理功能，确保数据的一致性和可靠性。 #### 数据库访问 AERONET数据库可通过项目网站访问，用户可以通过简单的注册流程获得访问权限。该数据库包含了来自全球各地监测站点的大量气溶胶观测数据，对于从事大气科学研究、气候模型验证以及卫星遥感数据校验的科研人员来说是极其宝贵的资源。 #### 应用领域 AERONET的数据广泛应用于多个科学领域，包括但不限于： - **气溶胶输送与辐射预算研究**：通过分析不同地区的气溶胶分布情况，研究其对气候变化的影响。 - **辐射传输建模**：用于改进和验证辐射传输模型，特别是在评估气溶胶对地球辐射平衡的影响时尤为重要。 - **卫星遥感数据验证**：AERONET提供的地面实测数据可用于校验卫星观测结果的准确性。 AERONET不仅为科学研究提供了宝贵的观测数据，而且通过其开放的合作模式促进了国际间的科学交流与合作，为解决全球性的环境问题做出了重要贡献。

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AERONET—A Federated Instrument Network

and Data Archive for Aerosol Characterization

B. N. Holben,* T. F. Eck,

†

I. Slutsker,

‡

D. Tanre

J. P. Buis,

A. Setzer,

E. Vermote,** J. A. Reagan,

††

Y. J. Kaufman,* T. Nakajima,

‡‡

F. Lavenu,

§§

I. Jankowiak,

and A. Smirnov

‡

he concept and description of a remote sensing aerosol dardization for these measurements. The system’s auto-

monitoring network initiated by NASA, developed to sup-

matic data acquisition, transmission, and processing fa-

port NASA, CNES, and NASDA’s Earth satellite systems

cilitates aerosol characterization on local, regional, and

under the name AERONET and expanded by national

global scales with applications to transport and radiation

and international collaboration, is described. Recent de-

budget studies, radiative transfer-modeling and valida-

velopment of weather-resistant automatic sun and sky

tion of satellite aerosol retrievals. This article discusses

scanning spectral radiometers enable frequent measure-

the operation and philosophy of the monitoring system,

ments of atmospheric aerosol optical properties and pre-

the precision and accuracy of the measuring radiometers,

cipitable water at remote sites. Transmission of automatic

a brief description of the processing system, and access

measurements via the geostationary satellites GOES and

to the database. Elsevier Science Inc., 1998

METEOSATS’ Data Collection Systems allows reception

and processing in near real-time from approximately 75%

of the Earth’s surface and with the expected addition of

INTRODUCTION

GMS, the coverage will increase to 90% in 1998. NASA

Accurate knowledge of the spatial and temporal extent

developed a UNIX-based near real-time processing, display

of aerosol concentrations and properties has been a limi-

and analysis system providing internet access to the emerg-

tation for assessing their influence on satellite remotely

ing global database. Information on the system is avail-

sensed data (Holben et al., 1992) and climate forcing

able on the project homepage, http://spamer.gsfc.nasa.gov.

(Hansen and Lacis, 1990). With the exception of the

The philosophy of an open access database, centralized

AVHRR weekly ocean aerosol retrieval product (Rao et

processing and a user-friendly graphical interface has

al., 1989), the voluminous 20-year record of satellite data

contributed to the growth of international cooperation

has produced only regional snapshots of aerosol loading,

for ground-based aerosol monitoring and imposes a stan-

and none have yielded a database of the optical proper-

ties of those aerosols that are fundamental to our under-

* NASA/Goddard Space Flight Center, Greenbelt

standing of their influence on climate change. With the

† Hughes STX Corporation, Code 923, NASA/GSFC, Greenbelt

advent of the EOS era of laboratory quality orbiting

‡ Science Systems and Applications Inc., Code 923, NASA/

GSFC, Greenbelt

spectral radiometers, new algorithms for global scale

§ Laboratoire d’Optique Atmosphe

rique, U.S.T. de Lille, Villen-

aerosol retrievals and their application for correction of

euve d’Ascq, France

remotely sensed data will be implemented (Kaufman and

k CIMEL Electronique, Paris, France

¶ Instituto de Pesquisas Espaciais, Sao Jose

dos Campos, Brazil

Tanre

, 1996). However, the prospect of fully understand-

** University of Maryland, NASA/GSFC, College Park

ing aerosols influence on climate forcing is small without

†† University of Arizona, Tucson

validation and augmentation by ancillary ground-based

‡‡ University of Tokyo, Komaba, Meguro-ku, Tokyo, Japan

§§ Laboratoire d’Ecologie, Ecole Normale Superieure, Paris,

observations as can be provided by radiometers histori-

France

cally known as sun photometers. Following is a descrip-

Address correspondence to Brent Holben, NASA/GSFC, Code

tion of a new Sun–sky scanning radiometer system that

923, Greenbelt, MD 20771. E-mail: brent@kratmos.gsfc.nasa.gov

Received 30 May 1997; revised 12 February 1998.

standardizes ground-based aerosol measurements and pro-

REMOTE SENS. ENVIRON. 66:1–16 (1998)

Elsevier Science Inc., 1998 0034-4257/98/$19.00

655 Avenue of the Americas, New York, NY 10010 PII S0034-4257(98)00031-5

Holben et al.

cessing, can provide much of the ground-based validation knowledge base most importantly through inversion of

the sky radiances to derive aerosol microphysical proper-data required for future remote sensing programs and may

provide basic information necessary for improved assess- ties such as size distribution and optical properties such

as phase function (Nakajima et al., 1983; 1996; Tanre

etment of aerosols impact on climate forcing.

al., 1988; Shiobara et al., 1991; Kaufman et al., 1994).

This technique requires precise aureole measurements

BACKGROUND

near the solar disk and good straylight rejection. Histori-

cally these systems are rather cumbersome, not weather-The technology of ground-based atmospheric aerosol

measurements using sun photometry has changed sub- hardy, and expensive. The CIMEL and PREDE (French

and Japanese manufacturers, respectively) Sun and skystantially since Volz (1959) introduced the first handheld

analog instrument almost 4 decades ago. Modern digital scanning spectral radiometers overcome most such limi-

tations, and provide retrievals from direct Sun measure-units of laboratory quality and field hardiness can collect

data more accurately and quickly and are often inter- ments of aerosol and water vapor abundance in addition

to aerosol properties from inversion of spectral sky radi-faced with onboard processing (Schmid et al., 1997; Eh-

sani et al., 1998; Forgan, 1994; Morys et al., 1998). The ances. Since the measurements are directional and rep-

resent conditions of the total column atmosphere, theremethod used remains the same, that is a filtered detector

measures the spectral extinction of direct beam radiation are direct applications to satellite and airborne observa-

tions as well as atmospheric processes.according to the Beer–Lambert–Bouguer law:

As has been demonstrated by the shadowband net-

⫽V

exp(s

(1)

work and satellite remote sensing in general, prompt de-

where

livery of the data for analysis is fundamental for ob-

taining a comprehensive, continuous database, and allows

V⫽digital voltage,

assessment of the collecting instruments health and cali-

⫽extraterrestrial voltage,

bration. To achieve this goal, minimize costs and expand

m⫽optical air mass,

the coverage globally, we use the simple and inexpensive

s⫽total optical depth,

Data Collection System (DCS) operating on the geosyn-

k⫽wavelength,

chronous GOES, METEOSAT, and GMS satellites pro-

d⫽ratio of the average to the actual Earth–Sun

viding nearly global coverage in near real-time at very

distance,

little expense (NOAA/NESDIS, 1990).

⫽transmission of absorbing gases.

Finally there are the very contentious issues of pro-

The digital voltage (V) measured at wavelength (k)isa

cessing the data archive. Although the Beer–Lambert–

function of the extraterrestrial voltage (V

) as modified

Bouguer law is very straightforward, its implementation

by the relative Earth–Sun distance (d), and the exponent

has as many variations as there are investigators who use

of the total spectral optical depth (s

) and optical air

it. The central problem being agreement on the accuracy

mass (m). The total spectral optical depth is the sum of

by which the aerosol optical thickness is derived. The un-

the Rayleigh and aerosol optical depth after correction

certainties in computation of the air mass (m), the calcu-

for gaseous absorption.

lations for the Rayleigh and ozone optical depths (s

, s

The multifilter rotating shadowband radiometer

and water vapor expressed as total column abundance or

(MFRSR) employs a different strategy. It measures spec-

precipitable water (Pw) as well as strategies for calibra-

tral total and diffuse radiation to obtain the direct com-

tion of the instruments and monitoring the long-term

ponent from which aerosol optical thickness is computed

change in calibration all combine to preclude any glob-

using the Beer–Lambert–Bouguer law. The instrument

ally accepted processing scheme. Perhaps even more de-

nominally measures at 1-min intervals and has been

batable are the aerosol properties derived from inver-

shown to be reliable over long periods of time. The mea-

sions of the sky radiances with the radiation transfer

surements are networked to a common server by a mo-

equation. Our solutions make the raw data and calibra-

dem interface and the data processed by a common anal-

tion data available to the user and provide a basic pro-

ysis system (Harrison et al., 1994). It is widely used in

cessing package (of published, widely accepted algo-

the United States principally for the DOE ARM sites. As

rithms) with sufficient friendliness and flexibility that all

the number of measurements from the MFRSR network

data may be accessed globally through common forms of

increases, the impact of aerosol loading on the radiation

electronic communication on the internet.

balance should be more clearly understood, especially

Following is the Aerosol Robotic Network (AERO-

when taken in concert with other ground, airborne, and

NET) version of a ground-based aerosol monitoring sys-

satellite measurements.

tem that offers a standardization for a ground-based

Sky scanning spectral radiometers, that is, radiome-

regional to global scale aerosol monitoring and character-

ters that measure the spectral sky radiance at known an-

ization network. We have assembled a reliable system

and offer it as a point of focus for further developmentgular distances from the Sun, have expanded the aerosol

AERONET—Aerosol Monitoring Network

of each component. As an example of the system’s per- allowing compensation for any temperature dependence

in the silicon detector. A polarization model of the CE-formance under a variety of conditions, we present data

collected in the Brazilian Amazon during the dry season 318 is also used in AERONET. This version executes the

same measurement protocol as the standard model butand Mauna Loa, Hawaii. Owing to the fundamental im-

portance of these and similar data for basic aerosol re- takes additional polarized solar principal plane sky radi-

ance measurements hourly at 870 nm (Tables 1 and 2).search, aerosol forcing research and validation of retriev-

als from space-based platforms, we are emphasizing this The sensor head is pointed by stepping azimuth and

zenith motors with a precision of 0.05⬚. A microprocessorsystem for a regional to global scale network of these ob-

servations. Our philosophy is for an open, honor system computes the position of the Sun based on time, latitude,

and longitude, which directs the sensor head to withinwhereby all contributed data may be accessed by anyone,

but publication of results requires permission of the con- approximately 1⬚ of the Sun, after which a four-quadrant

detector tracks the Sun precisely prior to a programmedtributing investigators. We have designed and imple-

mented a system that promotes these goals. measurement sequence. After the routine measurement

is completed, the instrument returns to the “park” posi-

tion awaiting the next measurement sequence. A “wet

AUTOMATIC SUN AND SKY SCANNING

sensor” exposed to precipitation will cancel any measure-

SPECTRAL RADIOMETER

ment sequence in progress. Data are downloaded under

program control to a Data Collection Platform (DCP)

Most if not all sun photometer networks have had lim-

typically used in the geostationary satellite telemetry sys-

ited success when people are required to make routine

observations. Therefore, an automatic instrument is a fun- tem (see Data Transmission section).

damental component for routine network observations.

The measurement protocol must be reasonably robust

Measurement Concept

such that unwanted data may be successfully screened

Since the instrument was first available in 1992, the mea-

from useful data, data quality, and instrument functional-

surement protocols have evolved to a point in which we

ity may be evaluated and the instrument should be self-

feel maximum information content is achieved within the

calibrating or at the least collects data for its calibration.

constraints of the hardware and software available for the

Following is our assessment of the CIMEL CE-318 in-

network system and the goals of the aerosol climatology

strument that meets these criteria of a field hardy, trans-

data base. The radiometer makes only two basic mea-

mitting, Sun, and sky scanning spectral radiometer which

surements, either direct Sun or sky, both within several

is used in the AERONET program.

programmed sequences. The direct Sun measurements

are made in eight spectral bands (anywhere between 340

General Description

nm and 1020 nm; 440 nm, 670 nm, 870 nm, 940 nm,

and 1020 nm are standard) requiring approximately 10 s.The CIMEL Electronique 318A spectral radiometer

manufactured in Paris, France is a solar-powered weather A sequence of three such measurements are taken 30 s

apart, creating a triplet observation per wavelength. Trip-hardy robotically pointed sun and sky spectral radiome-

ter. This instrument has approximately a 1.2⬚ full angle let observations are made during morning and afternoon

Langley calibration sequences and at standard 15-min in-field of view and two detectors for measurement of di-

rect sun, aureole, and sky radiance. The 33 cm collima- tervals in between (Table 1). The time variation of clouds

are typically greater than that of aerosols, causing an ob-tors were designed for 10

⫺

straylight rejection for mea-

surements of the aureole 3⬚ from the sun. The robot- servable variation in the triplets that can be used to

screen clouds in many cases. Additionally the 15-min in-mounted sensor head is parked pointed nadir when idle

to prevent contamination of the optical windows from terval allows a longer temporal frequency check for

cloud contamination.rain and foreign particles. The Sun/aureole collimator is

protected by a quartz window allowing observation with Sky measurements are performed at 440 nm, 670 nm,

870 nm, and 1020 nm (Table 1). A single spectral mea-a UV enhanced silicon detector with sufficient signal-

to-noise for spectral observations between 300 nm and surement sequence (Langley sky) is made immediately

after the Langley airmass direct Sun measurement, 20⬚1020 nm. The sky collimator has the same field of view,

but an order of magnitude larger aperture-lens system from the Sun. This is used to assess the stability of the

Langley plot analysis according to O’Neill and Millerallows better dynamic range for the sky radiances. The

components of the sensor head are sealed from moisture (1984). Two basic sky observation sequences are made,

the “almucantar” and “principal plane.” The philosophyand desiccated to prevent damage to the electrical com-

ponents and interference filters. Eight ion-assisted depo- is to acquire aureole and sky radiances observations

through a large range of scattering angles from the Sunsition interference filters are located in a filter wheel

which is rotated by a direct drive stepping motor. A through a constant aerosol profile to retrieve size distri-

bution, phase function, and aerosol optical thicknessthermister measures the temperature of the detector

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