Climate Lab Research

Jump: Aerosol Remote Sensing and Modeling, Cloud Remote Sensing and Modeling, Water Cycle and Precipitation, Solar Radiation, Surface Properties, Climate Analysis, Radiative Transfer

 Aerosol Remote Sensing and Modelingtop

The Climate and Radiation Lab (CRL) has a very active group studying the climate and health impacts of airborne particles (“aerosols”). Aerosol particles reflect sunlight, which tends to cool surfaces locally. Some also absorb sunlight, warming and stabilizing the ambient atmosphere while still cooling the surface below, sometimes suppressing cloud formation, and even affecting large-scale atmospheric circulation. In addition, aerosols are essential participants in the formation of cloud droplets and ice crystals, functioning as the collectors of water vapor molecules during the initial stages of cloud development. Particle abundance and properties affect the brightness, thickness, and possibly lifetimes of clouds and ultimately, precipitation and the terrestrial water cycle. And in significant near-surface concentrations they are pollutants, reducing visibility and raising health risks for those exposed. more...

 Cloud Remote Sensing and Modelingtop

Clouds play a critical role in the Earth's hydrologic cycle and in the energy balance of the climate system. They have a strong effect on solar heating by reflecting part of the incident solar radiation back to space. Clouds also reduce the planet’s ability to cool by intercepting part of the thermal infrared radiation emitted by the surface and atmosphere below the cloud, and re-emitting a fraction of this radiation back to the surface. Global changes in surface temperature are highly sensitive to cloud amount and type, it is therefore not surprising that the largest uncertainty in model estimates of global warming is due to clouds. more...

 Water Cycle and Precipitationtop

70% of the Earth’s surface is covered by oceans. It is the only inner planet where all three phases of water (liquid, ice, and vapor) coexist. The movement of water in its different forms, and the perpetual water phase changes are essential ingredients of the planetary water cycle (also known as the hydrological cycle). Precipitation is a major component of the water cycle, and is responsible for most of the fresh water on the planet. It occurs when water vapor levels in the atmosphere reach saturation upon which water vapor condenses or deposits on small particles called condensation/ice nuclei to form clouds consisting of suspended liquid or ice particles or a mixture of both. Under appropriate conditions larger liquid and ice particles form that fall to the surface as precipitation due to gravity. Precipitation is associated with a vast range of weather events: tropical cyclones, thunderstorms, frontal systems, drizzle, snowfall, etc. more...

 Solar Radiationtop

The Sun’s illumination is the ultimate energy source for the Earth's biosphere, and the ultimate driving force for atmospheric, and oceanic circulations. The Sun is a variable star as one can see from sunspots recorded back to Galileo’s time in the early 1600s. Satellite observations over the past three decades show that the sunspot activity is associated with changes in solar output energy. The total solar irradiance (TSI), improperly called “solar constant” until a few years ago, has been found to change about 0.1% in an 11-year solar sunspot activity. The current most accurate TSI values from the Total Irradiance Monitor (TIM) on NASA’s Solar Radiation and Climate Experiment ( SORCE ) is 1360.8 ± 0.5 W/m2 during the 2008 solar minimum as compared to previous estimates of 1365.4 ± 1.3 W/m2 established in the 1990s.  more...

 Surface Propertiestop

The reflectance of natural surfaces depends on the view geometry, i.e., the position of the observer or measuring instrument relative to the Sun. Land surfaces usually appear darker in the forward scattering direction (i.e, with the Sun in front of the observer) and significantly brighter in the backscattering direction (i.e., with the Sun behind the observer). This dependence arises to a large extent from the 3-D structure or roughness of the surface as the end result of the interplay between shadowed and sunlit facets. For example, shadows are absent in the backscattering direction, which creates a reflectance “hot spot,” whereas they are maximal in the forward scattering direction, effectively darkening the surface. Solar photons may also be trapped bouncing between surface elements such as tree leaves before escaping. The number of such "internal" scattering events is modulated by the general brightness of the surface, creating additional angular dependence. Snow, the brightest type of surface at visible wavelengths, has maxima at both forward and backscattering angles, whereas water reflects light primarily in the forward scattering, or “glint,” direction. Wind roughens water surface, creating waves; stronger wind speeds lead to steeper waves, widening the glint "cone" and reducing its peak brightness. more...

 Climate Analysistop

The goal of climate analysis is to better understand the Earth’s past and present climate, and to predict future climate response to changes in natural and human-induced factors, such as the Sun, greenhouse gases (e.g., water vapor, carbon dioxide and methane), and aerosols (e.g., from dust storms, pollution, fires, sea spray or volcanic eruptions). Climate analysis studies are routinely carried out using a mix of data from diverse sources including historical climate data, current and past satellite instruments, field campaigns, and outputs from regional and global numerical models. more...

 Radiative Transfertop

The Sun is a distant source of energy that reaches the Earth as solar radiation. Solar radiation has a rich spectral structure. It consists of ultra-violet radiation largely absorbed by stratospheric ozone, visible radiation to which the atmosphere is mostly transparent, and near-infrared and solar infrared radiation where some absorption by atmospheric water vapor occurs. In addition to solar radiation, the spectral region of longer-wavelength thermal-infrared radiation dominated by terrestrial sources is equally important for weather and climate. Scientists in the Climate and Radiation Lab (CRL) study the individual spectral regions of solar and thermal radiation as well as the propagation of total (also known as “broadband”) shortwave and longwave fluxes to better understand the Earth’s radiation budget. The total solar flux across all wavelengths reaching the Earth is ≈ 1361 W/m2, a number that matters tremendously for the Earth’s climate. Its slight variations are monitored as continuously and accurately as possible from space by missions such as the SOlar Radiation and Climate Experiment (SORCE) whose Project Scientist is a CRL member. more...