On the Global Contrasting Temperature-Precipitation Phase Mechanisms in the Last Century

Global precipitation patterns have changed compared to the before 1960 (pre-industrial period). By now the temperature has risen by approximately 1°C. The atmospheric heat-retaining constituents have been raised by human-induced activities. It is influencing the composition of the atmospheric gases and water vapour leading to tropospheric energy budget imbalance affecting atmospheric pressure systems. Increased atmospheric warming leads water holding capacity to rise. Such changes insinuated contrasting phases: decreased (increased) temperature- increased (decreased) precipitation in the last century. Mechanisms of these in- and out- phases are investigated. In the total four (two colder-wet and two warmer-dry) global conditions are observed. These time slices indicate a gradual increase in global temperature and a decrease in precipitation. Clausius-Clapeyron relation suggests abrupt warming and increased water vapour pressure in recent decades. In addition, the global climate system is shifting towards abnormal warm-wet or warm-dry conditions. Further, contrasting changes in global precipitation have been seen, in particular after 1960 (post-industrial period). It is significantly noted that there has been a global contrasting temperature-precipitation phase mechanism in the last century.

A holistic framework to estimate the origins of atmospheric moisture and heat using a Lagrangian model

Despite the existing myriad of tools and models to assess atmospheric source–receptor relationships, their uncertainties remain largely unexplored and arguably stem from the scarcity of observations available for validation. Yet, Lagrangian models are increasingly used to determine the origin of precipitation and atmospheric heat, scrutinizing the changes in moisture and temperature along air parcel trajectories. Here, we present a holistic framework for the process-based evaluation of atmospheric trajectories to infer source–receptor relationships of both moisture and heat. The framework comprises three steps: (i) the diagnosis of moisture and heat from Lagrangian trajectories using multi-objective criteria to evaluate the accuracy and reliability of the fluxes, (ii) the attribution of sources following mass- and energy-conserving algorithms in order to establish source–receptor relationships, and (iii) the bias correction of diagnosed fluxes and the corresponding source–receptor relationships. Applying this framework to simulations from the Lagrangian model FLEXPART, driven with ERA-Interim reanalysis data, allows us to quantify the errors and uncertainties associated with the resulting source–receptor relationships for three cities in different climates (Beijing, Denver and Windhoek). Our results reveal large uncertainties inherent in the estimation of heat and precipitation origin with Lagrangian models, but they also demonstrate the synergistic impacts of source- and sink bias-corrections. The proposed framework paves the way for a cohesive assessment of the dependencies in source–receptor relationships.

Radiative and Dynamic Controls on Atmospheric Heat Transport over Different Planetary Rotation Rates

Atmospheric heat transport is an important piece of our climate system, yet we lack a complete theory for its magnitude or changes. Atmospheric dynamics and radiation play different roles in controlling the total atmospheric heat transport (AHT) and its partitioning into components associated with eddies and mean meridional circulations. This work focuses on two specific controls: a radiative one, namely atmospheric radiative temperature tendencies, and a dynamic one, the planetary rotation rate. We use an idealized gray radiation model to employ a novel framework to lock the radiative temperature tendency and total AHT to climatological values, even while the rotation rate is varied. This setup allows for a systematic study of the effects of radiative tendency and rotation rate on AHT. We find that rotation rate controls the latitudinal extent of the Hadley cell and the heat transport efficiency of eddies. Both the rotation rate and radiative tendency influence the strength of the Hadley cell and the strength of equator–pole energy differences that are important for AHT by eddies. These two controls do not always operate independently and can reinforce or dampen each other. In addition, we examine how individual AHT components, which vary with latitude, sum to a total AHT that varies smoothly with latitude. At slow rotation rates the mean meridional circulation is most important in ensuring total AHT varies smoothly with latitude, while eddies are most important at rotation rates similar to, and faster than, those of Earth.

Super Sites for Advancing Understanding of the Oceanic and Atmospheric Boundary Layers

Air‐sea interactions are critical to large-scale weather and climate predictions because of the ocean's ability to absorb excess atmospheric heat and carbon and regulate exchanges of momentum, water vapor, and other greenhouse gases. These exchanges are controlled by molecular, turbulent, and wave-driven processes in the atmospheric and oceanic boundary layers. Improved understanding and representation of these processes in models are key for increasing Earth system prediction skill, particularly for subseasonal to decadal time scales. Our understanding and ability to model these processes within this coupled system is presently inadequate due in large part to a lack of data: contemporaneous long-term observations from the top of the marine atmospheric boundary layer (MABL) to the base of the oceanic mixing layer.We propose the concept of “Super Sites” to provide multi-year suites of measurements at specific locations to simultaneously characterize physical and biogeochemical processes within the coupled boundary layers at high spatial and temporal resolution. Measurements will be made from floating platforms, buoys, towers, and autonomous vehicles, utilizing both in-situ and remote sensors. The engineering challenges and level of coordination, integration, and interoperability required to develop these coupled ocean‐atmosphere Super Sites place them in an “Ocean Shot” class.

Atmosphere-Ocean compound heat wave events in the Eastern Mediterranean

<p>Mediterranean marine heat waves (MHW) can be defined as abrupt but prolonged, discrete and anomalously warm water events that last for five or more days and exceed temperatures warmer than the 99th percentile (Darmaraki et al. 2019). Like their atmospheric counterpart, Mediterranean MHW have already increased in intensity, frequency and duration - a trend projected to continue under anthropogenic climate change. Recent observations of MHW demonstrated a strong influence of these extreme climatic events on marine organisms, including mass mortalities and shifts in species ranges but also economic impacts on fisheries and aquaculture. MHW can be caused by a combination of atmospheric and oceanic processes and depend on the specific season and location of occurrence. However, the main triggers are generally still not well understood and the current knowledge is largely based on these reported regional impacts. This work focuses on historical (1985 – 2014) atmospheric and marine heat waves in a high resolution CMIP6 model as well as a fully three-dimensional oceanographic hindcast of the interconnected Eastern Mediterranean – Black Sea system. We detect the atmospheric and marine heatwaves and investigate the triggering, compound/concurrent effect of the atmosphere on marine heat waves in the Eastern Mediterranean. For the analysis of atmospheric heat waves, we follow the methodology of Kuglitsch et al. (2010). We use Eastern Mediterranean atmospheric model and ERA-Interim reanalysis to calculate daily maximum (TX) and minimum (TN) air temperatures as well as to set temperature thresholds to estimate the beginning and end of the heat wave events. We identify MHWs from daily sea surface temperatures, applying the approach of Darmaraki et al. (2019). Furthermore, we calculate the heat wave frequency, duration and intensity. The two pairs of datasets are then compared with respect to the spatio-temporal occurrence of heat waves in the atmosphere and ocean, in an effort to reveal feedbacks between the two spheres which would characterize the events as compound. Finally, we estimate a threshold at which an atmospheric heat wave triggers a marine heat wave, and thus a compound event.</p>