Coordinated Upper-Troposphere-to-Stratosphere Balloon Experiment in Biak

Abstract

The stratospheric response to climate forcing, such as an increase of greenhouse gas, is often unpredictable because of interaction between radiation, dynamics, and chemistry. Climate models are unsuccessful in simulating the realistic distribution of stratospheric water vapor. The long-term trend of the stratospheric age of air (AoA), a measure that characterizes the stratospheric turnover time, remains inconsistent between diagnoses in climate models and estimates from tracer observations. For these reasons, observations designed specifically to distinguish the effects of individual contributing processes are required. Here, we report on CUBE/Biak, an observation campaign organized in Indonesia. Being inside the "tropical pipe" makes it possible to study the dehydration in the tropical tropopause layer and the gradual ascent in the stratosphere while minimizing the effects of multiple circulation pathways and wave mixing. Cryogenic sampling of minor constituents and major isotopes was conducted simultaneously with radiosonde observations of water vapor, ozone, aerosols, and cloud particles. The water vapor "tape recorder", gravitational separation, and isotopocules are being studied in conjunction with tracers that are accumulated in the atmosphere as dynamical and chemical measures of elapsed time since stratospheric air entry. The observational estimates concerning the AoA and water vapor tape recorder are compared with those derived from trajectory calculations. (Fig. 1). 69Why do we need CUBE/Biak? 70The atmospheric water content falls sharply toward the upper troposphere in response to 71 the decrease of temperature and associated drop of saturation water vapor pressure (Clausius- 72Clapeyron equation) with respect to height. As the air entering the stratosphere must cross the 73 cold tropopause, the stratosphere is extremely dry; water molecules constitute only 4 parts per 74 million. As a strong greenhouse gas, however, stratospheric water could drive decadal-scale per- 84Further investigation of radiosonde temperature data lead to a hypothesis, the "stratospheric 136Acceleration or deceleration of the BDC can be diagnosed by the decrease or increase of the age 137 of air (AoA), the time elapsed since stratospheric air made its final contact with the troposphere 138 (Kida 1983). We trace air parcels following atmospheric motion in the Lagrangian framework. 139The difficulty lies in the fact that, due to eddy mixing, any stratospheric air parcel is composed 140 of various infinitesimal elements that have followed different pathways since stratospheric entry 141 (Kida 1983; Hall and Plumb 1994; Waugh and Hall 2002). The distribution of transit times of all 142 infinitesimal elements that constitute an air parcel is the age spectrum. It is not observable. 143The mean value of stratospheric AoA, simply "mean age" hereafter, can be estimated by suc- 158An important piece missing in the analysis of Engel et al. (2009) was observational data in the 159 tropical stratosphere. As compared to mid...

Age and gravitational separation of the stratospheric air over Indonesia

“…To measure the CO 2 and SF 6 mole fractions, δ 15 N of N 2 , δ 18 O of O 2 , and δ(Ar/N 2 ) in the equatorial stratosphere, we conducted whole air sampling with balloon-borne cryogenic samplers over Biak, Indonesia in February 2015 as part of an observation campaign called "Coordinated Uppertroposphere-to-stratosphere Balloon Experiment in Biak" (CUBE/Biak; Hasebe et al, 2018) in cooperation with the National Institute of Aeronautics and Space of the Republic of Indonesia (LAPAN). In this paper, we present measured vertical profiles of the CO 2 and SF 6 mole fractions, δ 15 N of N 2 , δ 18 O of O 2 , and δ(Ar/N 2 ) and discuss some of the implications of these measurements on the age and gravitational separation of stratospheric air.…”

Reply to the referee #2

“…In the present study, air sampling was performed during balloon ascent. In the past, we conducted a number of similar air samplings using a cryogenic sampler with liquid helium (Honda et al, 1996) in which we collected samples during the balloon ascent and descent over Japan; they showed that the outgassing from the balloon and payload had a negligibly small impact on the air sample quality even if air sampling was made during the balloon ascent (Morimoto et al, 2009;. One sampler assigned to 21 km leaked after landing due to a defect in electric circuit.…”

Three-dimensional simulation of stratospheric gravitational separation using the NIES global atmospheric tracer transport model

“…The modeled results are compared with measurements over the main climatic zones: the circumpolar regions, the temperate latitudes, and the tropical latitudes ( Table 2). The collection of stratospheric air samples using a balloon-borne cryogenic sampler was initiated in 1985 at the Sanriku Balloon Center of the Institute of Space and Astronautical Science (Nakazawa et al, 1995(Nakazawa et al, , 2002Aoki et al, 2003;Goto et al, 2017;Sugawara et al, 2018;Hasebe et al, 2018). The program has continued up to the present.…”

“…7-8) the observed profiles are mainly smooth and have smaller vertical fluctuation, apart from the uppermost level over Syowa station for 5/01/2004. Due to the limited availability of balloon launching facilities, only one air sampling has been conducted in the equatorial mid-stratosphere over Biak (Hasebe et al, 2018). The observed distribution can be explained by the mixing of large-scale NH and SH background values and long-range transport of CO 2 with convective lifting (Inai et al, 2018).…”