Co-evolution of carbon cycle and air quality fluxes constrained by CMS-Flux and MOMO-Chem assimilation systems

<p>Rapid regional changes in anthropogenic emissions in response to the COVID-19 pandemic have underscored the contribution of fossil fuel (FF) emission uncertainty to regional carbon budgets.  Typical methods for spatially-explicit FF emissions are dependent on national reporting, which can incur substantial latencies.  However, the concomitant changes in short-lived pollutants from common emission sources point to opportunities to develop independent low-latency estimates of fossil fuel emissions and to better understand anthropogenic processes. Here we combine state-of-the-art Multiple Model Multi Constituent chemical data assimilation system (MOMO-Chem) with bottom-up FF emissions to repartition the net carbon fluxes from the NASA Carbon Monitoring System Flux (CMS-Flux) project.  To that end, we implement a novel Kalman filtering algorithm that predicts emission ratio co-evolution of air quality (AQ) and carbon species.  Based upon top-down estimates of AQ emissions, FF CO2 emissions and uncertainties can be rapidly determined.  We show overall good agreement between predicted FF fluxes and the latest bottom-up inventories.  These data are in turn used to interpret the decadal evolution of CMS-Flux net carbon exchange.  This approach is an important step in quantifying both regional fossil fuel and natural carbon fluxes contributions to the atmospheric CO2 growth rate.</p>

Moderate Water Stress from Regulated Deficit Irrigation Decreases Transpiration Similarly to Net Carbon Exchange in Grapevine Canopies

To determine the effects of timing and extent of regulated deficit irrigation (RDI) on grapevine (Vitis vinifera) canopies, whole-canopy transpiration (TrV) and canopy conductance to water vapor (gc) were calculated from whole-vine gas exchange near key stages of fruit development. The vines were managed under three approaches to RDI: 1) standard industry practice (RDIS), or weekly replacement of 60% to 70% of estimated evapotranspiration (ET) for well-watered grapevines; 2) early additional deficit (RDIE), or one-half of RDIS applied between fruit set and veraison; and 3) late additional deficit (RDIL), or one-half of RDIS applied between veraison and harvest. Compared with RDIS, the additional deficits (RDIE, RDIL) reduced daily cumulative Trv by about 45% (RDIE) and about 48% [RDIL (57% by unit leaf area)]. Diurnal patterns of gc indicated consistent moderate water stress in all RDI regimens (gc ≈50–150 mmol·m−2·s−1). Under RDIE and RDIL, there were transient occurrences of severe water stress, indicated by gc declining below 50 mmol·m−2·s−1. Across the day, vines under RDIE and RDIL had lower gc than RDIS. Under all deficit regimens, TrV exhibited opposing hysteretic loops with solar radiation [photosynthetic photon flux (PPF)] and vapor pressure deficit (VPD), with less sensitivity to VPD in RDIE and RDIL. For a given value of VPD, TrV was higher in the morning than in the afternoon. For a given value of PPF, TrV was higher in the afternoon than in the morning. Single-leaf measurements of transpiration overestimated TrV by an average of 45%. Instantaneous water use efficiency (WUE) declined during midday at the pre- and postveraison measurements for all RDI regimens. Whole-canopy daily integrated WUE (WUEd) did not differ among regimens during the additional deficits because daily cumulative values of whole-vine net carbon exchange (NCEV) and TrV changed proportionally: by about 43% to 46% in RDIE relative to RDIS. The case was less clear-cut for RDIL, where NCEv declined by 33% and TrV by 48% relative to RDIS. However, WUEd did not differ significantly between the two. More substantial water deficits than those are currently practiced in the industry through RDI could be used for potential water savings in semiarid climates.