Workpackage 1:

Tropical aircraft field campaign

Introduction

StratoClim will conduct an aircraft field campaign in the Indian subcontinent to obtain measurements and data that until today have not been available to the scientific community. The Russian high-flying research aircraft M55-Geophysica will be equipped with a comprehensive set of instruments to capture high-quality data sets of the distribution of passive tropospheric and stratospheric tracers and reactive species, number densities, size distributions and chemical composition of aerosols and ice particles, aerosol backscatter and depolarisation, as well as meteorological base parameters (pressure, temperature, etc.) for the sub-tropical upper troposphere/lower stratosphere (UTLS) region. These data together with satellite observations, will be used to validate and improve process models and ultimately Earth System Models/Climate Chemistry Models.

The Aircraft

For probing the UTLS region, the high-altitude aircraft M55 Geophysica is the only available European platform. The aircraft was developed by Myasishchev Design Bureau and built by Smolensky aircraft plant in 1988. To date the M55 Geophysica is the only subsonic aircraft in Europe performing long endurance flight at altitudes up to 21 km.

Between 1996 and 2010 the aircraft has been employed successfully in many, mostly EU-funded, international measurement campaigns, including APE-POLECAT, APE-THESEO, APE-GAIA, APE-INFRA, several ENVISAT validation campaigns, EUPLEX, TRoCCiNOx, SCOUT-O3, AMMA-SCOUT-O3 and RECONCILE.

For StratoClim project the aircraft will be equipped with a state-of-the-art instrument suite including several new instruments in order to measure a complete set of trace species and parameters relevant for StratoClim, including H2O, O3, COS, SO2, H2SO4, CO, and CO2 and HCN, long-lived tracers, nitrogen oxides, active halogen species, as well as particle size distribution, optical properties and chemical composition.

Campaign location

The aircraft field campaign focuses on detailed observations of atmospheric transport and physical-chemical processes which dominate the input of air and aerosols into the (sub-)tropical stratosphere. During Northern Hemisphere summer the flux of air into the stratosphere mostly occurs in the Asian Monsoon region and during Northern Hemisphere winter mostly in the West Pacific region. The Asian Monsoon anticyclonic circulation is a stable phenomenon that develops regularly. With its clear boundaries and outflow patterns along with strongly polluted inflow it provides an optimal atmospheric laboratory for the M55 Geophysica payload given the operational range and capabilities of the aircraft and the traceability of the tropospheric pollutant signals through the UT and TTL into the stratosphere. The West Pacific region provides similar features as the Asian Monsoon region, but due to generally less pollution in that area probably with smaller signals in tracer fields and therefor somewhat larger uncertainties for related process studies.

Both, the Asian Monsoon and the West Pacific regions are extremely under-researched given their global importance. For these reasons the Asian Monsoon region (during Northern Hemisphere summer) is chosen as primary target.

The first phase campaign will be conducted from Kalamata Greece 22.8.-9.9.2016 with an objective of testing the new instruments and measuring the outflow from the decaying anticyclone. The second phase campaign will be carried out in July / August 2017 in the Indian, which is an optimal location in order to reach the central regions oflation as well as the strong convection regions in the Bay of Bengal and regions of major outflow towards the Arabian Sea.

Campaign planning and support

The project plans a deployment of around 17 measurement flights. Based on recent numerical simulation results of CMIP5 (Coupled Model Intercomparison Project Phase 5), CCMval (Chemistry-Climate Model Validation Activity) and CCMI (IGAC/SPARC Chemistry-Climate Modelling Initiative) and new studies early on during the project based on Chemistry-Transport Model (CTM) results as well as results derived from "nudged" CCM simulations for recent years), the global modelling team will help planning the field campaign. This approach ensures that campaign planning fully takes into account all considerations about how the additional measurements can support model improvements in the most efficient way.

There are two potential campaign strategies to be finally determined shortly before the campaign: Either the M55 Geophysica will carry out instrumented transfer flights from and to a Western European base to probe the latitudinal trace gas distribution and outflow signatures of convection over the Arabian region. Alternatively, we might focus all flights on the tropical region with changing flight objectives into different meteorological domains (and having non-instrumented transfers of the aircraft to its home base).

For planning of the aircraft deployments, several forecasting tools will be provided to make best use of the individual flights. State-of-the art flight planning tools will be available. Dedicated flight strategies for optimal characterisation of relevant processes will be developed and followed. Observational results will be compared to regional model simulations, CTMs and nudged runs from CCMs to develop or improve process parameterisation modules. These will be implemented in CCMs and compared to larger scale and global data sets generated from satellite and ground-based network measurements.

International collaboration

In order to characterise tropospheric sources (convective low-level inflow) and to complement tracer profiles (e.g. CO, CO2, H2O, aerosols) to lower altitudes, the deployment of a second aircraft (not to be financed from the project) will be very advantageous. Hereby, we may benefit from synergies with national programmes. The OMO mission of the German HALO aircraft was scheduled for the 2015 AM season in the Indian region. The HALO deployments will yield trace gas, cloud and aerosol compositions up to the upper troposphere that will be extremely valuable for the StratoClim studies at higher altitudes. Close contact with the OMO campaign coordinators is held. Also, close cooperation with local scientists (country of the mission base) will be sought providing further ground-based, sonde, or even aircraft measurements. Contacts to India (for AM activities) and the Philippines (for West Pacific activities) have been established already in this respect

A major international research activity was build up also for tropical measurements focussing on the Pacific and Indian Ocean in 2014-2016, with deployments of the UK BAe-146 (CAST) and NASA Global Hawk (ATTREX) in Guam in Jan/Feb 2014, possibly joined by the NCAR HIAPER plane (CONTRAST). The US SEAC4RS activity initially planned for Thailand in 2012 and later for summer 2013 from Singapore has been rescheduled to the Middle American region now. Therefore, StratoClim will be the first major UTLS aircraft campaign around the Asian Monsoon.

The unique Geophysica instrumentation will make the StratoClim campaign very complementary to these other field campaigns. StratoClim will closely cooperate with other activities wherever possible and contacts with all lead scientists have been established. The StratoClim field activities will be embedded into this international framework by coordinating flight activities, negotiating data sharing agreements and organising joint science meetings. StratoClim's model activities and large international activities will benefit mutually from each other, and StratoClim will ensure that Europe will play an important role in this emerging international research focus.