Tomoaki Nishizawa

The EarthCARE Satellite: The Next Step Forward in Global Measurements of Clouds, Aerosols, Precipitation, and Radiation

AbstractThe collective representation within global models of aerosol, cloud, precipitation, and their radiative properties remains unsatisfactory. They constitute the largest source of uncertainty in predictions of climatic change and hamper the ability of numerical weather prediction models to forecast high-impact weather events. The joint European Space Agency (ESA)–Japan Aerospace Exploration Agency (JAXA) Earth Clouds, Aerosol and Radiation Explorer (EarthCARE) satellite mission, scheduled for launch in 2018, will help to resolve these weaknesses by providing global profiles of cloud, aerosol, precipitation, and associated radiative properties inferred from a combination of measurements made by its collocated active and passive sensors. EarthCARE will improve our understanding of cloud and aerosol processes by extending the invaluable dataset acquired by the A-Train satellites CloudSat, Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and Aqua. Specifically, EarthCARE’s c...

Lidar network observations of tropospheric aerosols

Observations of tropospheric aerosols (mineral dust, air-pollution aerosols, etc.) and clouds are being conducted using a network of two-wavelength (1064nm, 532nm) polarization (532nm) lidars in the East Asian region. Currently, the lidars are operated continuously at 23 locations in Japan, Korea, China, Mongolia and Thailand. A real-time data processing system was developed for the network, and the data products such as the attenuated backscatter coefficients and the estimated extinction coefficients for non-spherical and spherical aerosols are generated automatically for online network stations. The data are used in the real-time monitoring of Asian dust as well as in the studies of regional air pollution and climate change.

Algorithm to Retrieve Aerosol Optical Properties From High-Spectral-Resolution Lidar and Polarization Mie-Scattering Lidar Measurements

We developed an algorithm to estimate the vertical profiles of extinction coefficients at 532 nm for three aerosol types that are water-soluble, soot, and dust particles, using the extinction and backscattering coefficients at 532 nm for total aerosols derived from high-spectral-resolution lidar (HSRL) measurements and the receiving signal at 1064 nm and total depolarization ratio at 532 nm measured with Mie scattering lidar (MSL). The mode radii, standard deviations, and refractive indexes for each aerosol component are prescribed by the optical properties of aerosols and clouds database; the optical properties for each aerosol component are computed from Mie theory on the assumption that their particles are spherical and homogeneous, except for dust. To consider the effect of nonsphericity, the dust lidar ratio at 532 nm is assumed to be 50 sr, the value that is reported for Asian dust from the other observational studies. We performed sensitivity study on retrieval errors. The errors in extinction coefficient for each aerosol component were smaller than 30% and 60% when the measurement errors were plusmn5% and plusmn 10%. We demonstrated the ability of the algorithm by applying to the HSRL + MSL data measured at Tsukuba, Japan. Plumes consisting of water-soluble aerosols, soot, dust, or their mixture were retrieved; these results were consistent with simulation with a global aerosol transport model. Introducing the dust lidar ratio significantly improved a correlation between the retrieved dust concentration and the aerosol depolarization ratio at 532 nm derived from HSRL + MSL than the use of spherical dust optical model in the retrieval.

Observation of Moisture Tendencies Related to Shallow Convection

AbstractTropospheric moisture is a key factor controlling the global climate and its variability. For instance, moistening of the lower troposphere is necessary to trigger the convective phase of a Madden–Julian oscillation (MJO). However, the relative importance of the processes controlling this moistening has yet to be quantified. Among these processes, the importance of the moistening by shallow convection is still debated. The authors use high-frequency observations of humidity and convection from the Research Vessel (R/V) Mirai that was located in the Indian Ocean ITCZ during the Cooperative Indian Ocean Experiment on Intraseasonal Variability/Dynamics of the MJO (CINDY/DYNAMO) campaign. This study is an initial attempt to directly link shallow convection to moisture variations within the lowest 4 km of the atmosphere from the convective scale to the mesoscale. Within a few tens of minutes and near shallow convection occurrences, moisture anomalies of 0.25–0.5 g kg−1 that correspond to tendencies on ...

Fluorescence from atmospheric aerosols observed with a multi-channel lidar spectrometer

A lidar for measuring fluorescence from atmospheric aerosols was constructed with a third harmonic Nd:YAG laser, a 1-m diameter telescope, and a 32-channel time-resolved photon-counting spectrometer system. Fluorescence spectrum and vertical distribution of fluorescent aerosols in the lower atmosphere were observed during the nighttime with excitation at 355 nm. Relatively strong broad fluorescence was observed from Asian dust and air-pollution aerosols transported from urban and industrial areas. Rough estimates of the fluorescence efficiency were given for these aerosols. The intensity of the total fluorescence over the spectral range from 420 to 510 nm was comparable to that of nitrogen vibrational Raman scattering. That indicates the possibility of making a compact Raman-Mie-fluorescence lidar for aerosol monitoring.

Analysis of dust events in 2008 and 2009 using the lidar network, surface observations and the CFORS model

The Asian dust events in 2008 (May 24–June 4 in 2008) and in 2009 (March 12–25, October 13–26, and December 15–28 in 2009) were analyzed with the lidar network observations, surface observations in China, Korea, Japan, and Mongolia, and with the chemical transport model CFORS. Transport of Asian dust and mixing of dust with air pollution aerosols were studied. The event of May 24 to June 4 in 2008 was a significant event unusually late in the spring dust season. The dust event of March 12–25, 2009 was an interesting example of elevated dust layer, and transport of dust from the elevated dust layer to the ground by the boundary layer activity was observed with the lidars and surface observations in Japan. The concentration of air pollution aerosols was relatively high during the dust event, and the results suggest that vertical structure as well as transport path is important for the mixing of dust and air pollution aerosols. The dust events in October and December 2009 were examples of dust events in autumn and winter. The online mode CFORS reproduced the observation data generally well, except for the event of May 24 to June 4 in 2008. The results of the fourdimensional variational assimilation of the lidar network data reproduced the dust concentration in Korea and Japan reasonably in that event.

Evolution of a lidar network for tropospheric aerosol detection in East Asia

Abstract. A regional elastic-scattering lidar network called Asian dust and aerosol lidar observation network (AD-Net) has operated for 15 years (since 2001) in East Asia. In this network, the extinction coefficient of aerosols below an altitude of 9 km is continuously obtained when conditions are clear; the coefficient is divided into two parts: dust extinction and spherical extinction coefficients. The dust extinction coefficient has been compared with several parameters measured by other instruments and utilized by various studies, including studies on the epidemiology of Asian dust. Recent expansion of the lidar system at some observatories allows more optical parameters to be retrieved at those observatories. All AD-Net products are used for monitoring global environmental change as an activity of global atmospheric watch lidar observation network.

Continuous Observations of Aerosol Profiles with a Two-Wavelength Mie-Scattering Lidar in Guangzhou in PRD2006

Abstract Continuous lidar observation was performed in Guangzhou, China, in the Pearl River Delta (PRD) observation campaign in July 2006 (PRD2006), using a two-wavelength Mie-scattering lidar (532 and 1064 nm) with a depolarization measurement channel at 532 nm. The profiles of the extinction coefficients at 532 nm were derived using the two-wavelength method. The planetary boundary layer (PBL) height and the cloud-base height were derived from the signals at 1064 nm. Two air pollution episodes occurred during the campaign, one on 10–12 July and the other on 22–24 July. Two events with a typhoon-driven flow of northern air occurred on 15 and 25 July. Elevated aerosol layers were observed at 1 km above ground level on 12 July and on 22 and 23 July. This layer was also observed by the lidar aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite (CALIPSO) at 0200 LT 23 July 2006 near Guangzhou. The distribution observed by CALIPSO and trajectory analysis revealed that the layer was probably genera...

Real-time observational evidence of changing Asian dust morphology with the mixing of heavy anthropogenic pollution

Natural mineral dust and heavy anthropogenic pollution and its complex interactions cause significant environmental problems in East Asia. Due to restrictions of observing technique, real-time morphological change in Asian dust particles owing to coating process of anthropogenic pollutants is still statistically unclear. Here, we first used a newly developed, single-particle polarization detector and quantitatively investigate the evolution of the polarization property of backscattering light reflected from dust particle as they were mixing with anthropogenic pollutants in North China. The decrease in observed depolarization ratio is mainly attributed to the decrease of aspect ratio of the dust particles as a result of continuous coating processes. Hygroscopic growth of Calcium nitrate (Ca(NO3)2) on the surface of the dust particles played a vital role, particularly when they are stagnant in the polluted region with high RH conditions. Reliable statistics highlight the significant importance of internally mixed, ‘quasi-spherical’ Asian dust particles, which markedly act as cloud condensation nuclei and exert regional climate change.

Characterization of aerosols in East Asia with the Asian Dust and Aerosol Lidar Observation Network (AD-Net)

Continuous observations of aerosols are being conducted with the Asian Dust and aerosol lidar observation Network (AD-Net). Currently, two-wavelength (1064 nm and 532 nm) polarization-sensitive (532 nm) lidars are operated at 20 stations in East Asia. At the primary stations (6 stations), nitrogen vibrational Raman scattering is also measured to obtain the extinction coefficient at 532 nm. Recently, continuous observations with a three-wavelength (1064 nm, 532 nm and 355 nm) lidar having a high-spectral-resolution receiver at 532 nm and a Raman receiver at 355 nm and polarization-sensitive receivers at 532 nm and 355 nm) was started in Tsukuba. Also, continuous observations with multi-wavelength Raman lidars are being prepared in Fukuoka, Okinawa Hedo, and Toyama. A data analysis method for deriving distributions of aerosol components (weak absorption fine (such as sulfate), weak absorption coarse (sea salt), strong absorption fine (black carbon), non-spherical (dust)) has been developed for these multi-parameter lidars. Major subjects of the current studies with AD-Net include data assimilation of multi-parameter lidars, mixing states of Asian dust with air pollution particulate matter, and validation of EarthCARE ATLID based on the aerosol component analysis method.