The need to characterize the increase and distribution of greenhouse gases is a first order scientific goal of the atmospheric composition and climate communities. The HIAPER Pole-to-Pole Observations (HIPPO) program will provide global, meridional coverage, via vertical profiles throughout the depth of the troposphere enabling closure and inversion of global budgets of critical greenhouse gases (e.g. carbon dioxide, CO2; carbon monoxide, CO; and methane, CH4), and related long-lived tracers and ratios (e.g. the oxygen/nitrogen ratio, O2/N2). This suite of chemical measurements, made from 80 N to 70 S, and repeated over approximately six monthly intervals, will provide a unique and definitive data set, to be used in inversion and other global modeling analyses of carbon cycle gases.
Observed gradients in the hemispheric concentrations of greenhouse gases are critical to our ability to predict the fate of anthropogenic emissions of carbon gases. Previous chemical transport modeling studies used to infer CO2 surface fluxes, sources and sinks have been generally constrained to using boundary layer CO2 concentrations. The field experiments will thus take advantage of transformative capabilities newly available to the atmospheric science community provided by the use of the HIAPER G-V aircraft platform.
This work is supported under the NSF Carbon and Water in the Earth System solicitation, an interdisciplinary funding opportunity from the Directorate of Geosciences.
HIPPO Motivation The HIPPO was designed advance undersanding of global sources, sinks and transport of atmospheric components that affect the climate of the earth: gases, small particles, and clouds. Measurements of the atmosphere use satellites for global coverage, and a network of remote surface station for long term measurements. These data cannot resolve the fine-grained vertical and horizontal structure of the atmosphere. HIPPO filled a critical gap by obtaining, for the first time, data that could resolve fine-scale structure in a fully globa context, spanning all seasons of the year. HIPPO undertook five major aircraft missions (Jan 2009, Nov. 2009, MarchApril 2010, June-July 2011, August-Sep2011), spanning the globe from the North Pole to the coastal waters of theAntarctic, in continuous profiling mode from 500 feet (150m) to 49,000 feet (14.8 km). Figure 1 shows images derived from the data of one HIPPO transect. • The specific objectives of the HIPPO program were to: 1) develop a new paradigm for atmospheric measurements, at once fine-grained, high frequency, global, and persistent; 2) identify and quantify surface fluxes and atmospheric transformation and removal processes for key atmospheric gases and black carbon; discover new features of trace gas and aerosol sources and global-scale transport; 3) critically test Earth System Models, such as those used to assess the carbon cycle and greenhouse gases in the IPCC; 4) quantitatively link measurements of the Total Column CO2 Observing Network (TCCON) to WMO World Gas standards for greenhouse gases, using in situ atmospheric measurements; and test satellite observations and retrievals. Summary of HIPPO accomplishments 1. Global aircraft mission demonstrated. HIPPO showed for the first time that atmospheric measurements could be successfully made traversing the entire globe in constant profiling mode, with no laboratory facilities available, from start to finish. This accomplishment opens the path for future atmospheric missions to obtain fine-grained, global observations that fully resolve the vertical structure of the atmosphere. 2. HIPPO observed profound longterm changes in the atmosphere and sharp contrasts between regions affected by humans and the ever-shrinking areas remote from human influence. These newly visible impacts of human endeavors help shape the public debate on fossil fuel use and agricultural sources of greenhouse gases (N2O, CH4). Prominent results include: Black carbon has a shorter lifetime in the atmosphere than adopted in IPCC models. Global concentrations and radiative effects on climate are much lower than model simulations (Fig. 2). This result may have signicant policy implications. In each summer season land biosphere north of 40N takes up about twice as much CO2 as in Earth System models, releasing twoice as much in fall and winter. The annual growth and decay in boreal regions has more than doubled since 1957. The reasons for this dramatic change are being sought. This result may change projections of future levels of CO2 in the atmsphere (Fig. 3). The surface waters of the Arctic Ocean produce methane, espcially in regions with broken fields of floating ice, and release it to the atmosphere. The emergence of open water in the Arctic Ocean has created a new source of this important greenhouse gas. The tropical regions of the world produce much more nitorous oxide (N2O), an important greenhouse gas, than known previously. This is probably an nfluence of intensive agriculture and fertilizer use in some rapidly developing tropical/subtropical countries. HIPPO made strong outreach efforts. Tens of thousands of people followed HIPPO activities through the HIPPO website (http://hippo.ucar.edu) and through social media. Nearly a dozen graduate students used HIPPO research in their PhD studies, and more than two dozen participated in various aspects of field work and data analysis. HIPPO data dissemination was innovative and effects. The architecture of the data download site was developed using new approaches and partnerships between PIs, CDIAC, and NCAR. The data architecture was designed to be simple and transparent, and value-added products were created. It has been very successful already in transferring the data to a broad audience. More than 23 papers have been published using HIPPO data, about half by collaborators not members of the Science Team. We anticipate that HIPPO data will generate new ideas and change old concepts regarding the societal issues around global change in atmospheric composition.
