Automated observation of sea surface eddy flux on a cruising ship

Sea surface eddy fluxes were evaluated with the eddy correlation method including ship motion correction for the wind vector components. Previous ship motion correction algorithm was revised as a simple scheme setting a motion sensor at the same place with the sonic anemometer. This revised eddy flux system was mounted as a routine continuous measurement system on the R/V 'Mirai' of Japan Marine Science and Technology Center. The first cruise was conducted at the tropical weatern Pacific in June 2000. Continuous sea surface fluxes were obtained and the data quality was checked with some parameters. This system is planned to be developed as a automated data processing system including ship motion correction and real-time flux evaluation system. These eddy fluxes can be integrated with the bulk fluxes and radiation fluxes to understand sea surface heat balance over the global ocean

Turbulent mixing and its impact on lower tropospheric moisture over tropical ocean

The variability of lower-tropospheric humidity is a crucial feature of the tropical climate. Among the processes that impact moisture budget, the vertical transport by turbulent mixing is generally overlooked. Using observations from CINDY/DYNAMO campaign, this is a first attempt to quantify it over the tropical ocean. Turbulent patches of ~100 m depth are observed in relation with large vertical gradients of specific humidity. Intense mixing is diagnosed within these intermittent patches. Three approaches are used to diagnose the overall effect of this intermittent turbulence. Large uncertainties on the corresponding eddy diffusivity coefficient arise from parameters hard to experimentally constrain. However, dry conditions are associated with steep moisture vertical gradients above the boundary layers. Owing to the uncertainties on the eddy diffusivity, these gradients can correspond to negligible or to significant moisture tendencies (~0.5-1 g kg-1 day-1) during the recovery following a dry intrusion or the preconditioning stage of an MJO

Pre-YMC観測期間中のMJO通過時に劇的に発達したスマトラ西岸沖バリアレイヤーの形成過程

日本気象学会2017年度秋季大会（2017年10月30日～11月2日, 北海道大学学術交流会館） / 発表番号: C101http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/

Observation of moisture tendencies related to shallow convection

Tropospheric 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 the order of 10-20 g kg-1 day-1 between 1 and 4 km are observed and are attributed to shallow convective clouds. On the scale of a few hours, shallow convection is associated with anomalies of 0.5-1 g kg-1 that correspond to tendencies on the order of 1-4 g kg-1 day-1 according to two independent datasets: lidar and soundings. This can be interpreted as the resultant mesoscale effect of the population of shallow convective clouds. Large-scale advective tendencies can be stronger than the moistening by shallow convection; however, the latter is a steady moisture supply whose importance can increase with the time scale. This evaluation of the moistening tendency related to shallow convection is ultimately important to develop and constrain numerical models

Pre-YMC観測期間中のMJO通過によるスマトラ西岸沖バリアレイヤーの発達

スマトラ西岸沖では、降水量増大に対応して10月から12月にかけてバリアレイヤーが深まることが、過去の統計的な研究から知られている(e.g. Qiu et al. 2012, GRL)。一方で、個別のMJOと対応した観測例はまだ少なく、月平均よりも細かい時間規模におけるバリアレイヤーの形成・変動過程は、十分に理解されていない。本研究では、2015年11月から12月に行われたPre-YMC観測キャンペーン中に捉えられたMJO(マッデンジュリアン振動)の通過時におけるバリアレイヤー構造の急変について調べた。日本気象学会2016年度秋季大会（2016年10月26日～28日, 名古屋大学東山キャンパス） / 発表番号: D103http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/

Pre-YMC中に観測されたMJO強制によって劇的に発達したスマトラ西岸沖バリアレイヤーの形成過程

要旨 ; 2017年度日本海洋学会秋季大会（2017年10月13日～17日, 仙台国際センター 会議棟、東北大学青葉山北キャンパス）http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/

The Mixed Layer Variations off the Western Coast of Sumatra Associated with the MJO Passage During the Pre-YMC and YMC

Poster session OS18-D4-PM1-P-024 | OS18-A018 / AOGS 15th Annual Meeting Asia Oceania Geosciences Society (3-8 Jun. 2018, Honolulu, Hawaii

Pre-YMC観測期間中のMJO通過時におけるスマトラ西岸沖バリアレイヤー構造の急変

要旨 ; 2016年度日本海洋学会秋季大会（2016年9月11日～15日, 鹿児島大学）http://www.godac.jamstec.go.jp/darwin/cruise/mirai/mr15-04/

Air-sea fluxes with a focus on heat and momentum

Turbulent and radiative exchanges of heat between the ocean and atmosphere (hereafter heat fluxes), ocean surface wind stress, and state variables used to estimate them, are Essential Ocean Variables (EOVs) and Essential Climate Variables (ECVs) influencing weather and climate. This paper describes an observational strategy for producing 3-hourly, 25-km (and an aspirational goal of hourly at 10-km) heat flux and wind stress fields over the global, ice-free ocean with breakthrough 1-day random uncertainty of 15 W m–2 and a bias of less than 5 W m–2. At present this accuracy target is met only for OceanSITES reference station moorings and research vessels (RVs) that follow best practices. To meet these targets globally, in the next decade, satellite-based observations must be optimized for boundary layer measurements of air temperature, humidity, sea surface temperature, and ocean wind stress. In order to tune and validate these satellite measurements, a complementary global in situ flux array, built around an expanded OceanSITES network of time series reference station moorings, is also needed. The array would include 500–1000 measurement platforms, including autonomous surface vehicles, moored and drifting buoys, RVs, the existing OceanSITES network of 22 flux sites, and new OceanSITES expanded in 19 key regions. This array would be globally distributed, with 1–3 measurement platforms in each nominal 10° by 10° box. These improved moisture and temperature profiles and surface data, if assimilated into Numerical Weather Prediction (NWP) models, would lead to better representation of cloud formation processes, improving state variables and surface radiative and turbulent fluxes from these models. The in situ flux array provides globally distributed measurements and metrics for satellite algorithm development, product validation, and for improving satellite-based, NWP and blended flux products. In addition, some of these flux platforms will also measure direct turbulent fluxes, which can be used to improve algorithms for computation of air-sea exchange of heat and momentum in flux products and models. With these improved air-sea fluxes, the ocean’s influence on the atmosphere will be better quantified and lead to improved long-term weather forecasts, seasonal-interannual-decadal climate predictions, and regional climate projections