41 Matching Annotations
  1. Feb 2021
    1. Such principles have recently been taken to efficiently model motion of water in the ocean and specifically predict sea surface tem-peratures. Here, the motion field was learned via a deep neural network, and then used to update the heat content and temperatures via phys-ically modelling the movement implied by the motion field

      (1) learning from sparse data, but directly related... using learned motion field (less obs. available in space and time) to directly predict SST via physical equations

      (2) learning from high-quality data, but more secondary... using learned thermo field (given more and high-quality data compared to motion field) and derive motion field to predict SST.

      How close will they be in SST prediction?

  2. Apr 2019
    1. Interestingly the dry experiment in their study maintains the steep −3 slope all the way to the mesoscale in the upper troposphere. This result emphasizes the critical role of moist convection in the creation of the shallower −5/3 slope.

      dry atmosphere is relatively trivial...

    1. Small, but unavoidable, relative errors on the largest scales at which the background kinetic energy spectrum follows a λ5/3 slope (100–400 km) can rapidly propagate downscale to the smallest resolved features in operational weather forecasts

      100-400 km, a scale of convective systems, so important!

    2. The growth of the KE spectra shown in Fig. 4 is certainly due to deep moist convection, but its detailed evolution does not particularly resemble a cascade in which energy spreads either upscale or downscale through progressive exchanges with nearby scales.

      Neither upscale or downscale cascade?

    3. Nevertheless, comparing both panels of Fig. 1, it is evident that butterflies will never be of practical importance because trivial relative errors in the large scales will overwhelm 100% relative errors on the very small scales.

      errors of small scales become saturated really fast, so it's not practical to pursue the accuracy there. A larger scale accuracy is what we can handle with.

    4. One important limitation on the accuracy of weather forecasts is imposed by unavoidable errors in the specification of the atmosphere’s initial state.

      butterfly effet

    1. Time evolution of the simulated (a) MSLP and (b) radius of the azimuthal-mean hurricane-force surface wind

      reminds me the gradient wind balance relationship in our 3-D toy tornado model assignment. In real cases, wind speed is not quite directly proportional to pressure.

    1. These terms are engineered to drive the mean vertical profile of virtual temperature toward a specified reference profile. This relaxation may be visualized as being the result of a mean vertical velocity profile which produces cooling via upward advection of potential temperature so as to counter the heating associated with condensation and radiation in the model.

      adjustment toward a reference profile

    2. The level of nondivergence separates vertically the inflow from the outflow, and its level strongly influences the values of sin and sout in these currents, and hence the value of δs.

      nondivergence level separates inflow from outflow. The lower this level is, the closer the inflow approaches to surface layers, inducing moisture convergence/ flux for spin-up.

    3. We used δθ = ±0.5, 1.0, and 2.0 K, where the “+” corresponds to warming in the upper troposphere, the “−” indicates cooling at lower levels.

      impose different degrees of stratiform heating as Fig. 2

    1. There can be no radiative-convective equilibrium unless /3 = 1, which in most implementations of Kuo-type schemes requires large-scale saturation through the entire column

      dq/dt = 0 --> steady state, RCE only exists as beta = 1. beta ~ large-scale relative humidity, so it's impossible to have RCE with a saturated atmosphere!

      A clear failure...

    1. Observations show that latent heating is positively correlated with temperature in disturbances found in the tropical western Pacific (i.e. they are not moist convectively damped)

      [Q'T']>0

    2. CISK more broadly interpreted has long acknowledged the important role of surface fluxes

      What I thought CISK and WIHSE before for TC intensification is latent heating versus surface flux, just two different sources. It seems that these two theorem are not entirely opposite..

    1. Arakawa and Schubert [1974] in which it is argued that moist convection constrains the “cloud work‐function” (a plume‐based counterpart to CAPE that considers entrainment) to be close to zero.

      ensemble clouds (with spectra of entrainment rates) consume CAPE --> cloud work-function (dCAPE/dt?), making it close to zero.

    2. Nine simulations are conducted, each with a different imposed CO2concentration in the range 1–1280 ppmv and a corresponding SST between 286 and 309 K

      does where we put the CO2 matter, in different levels?

    1. The particularnature of that moist adiabat is determined by the bulk properties of updrafts (includingthe microphysics of freezing and precipitation within them), and of downdrafts driven bythe evaporation of precipitation.

      how does bulk properties of downdrafts determine the moist adiabat? changing Tenv to approach neutral buoyancy?

      updraft --> heating upper layers --> reducing T-Tenv

      downdraft --> evaporatively cooling lower --> reducing T-Tenv?

    2. Three main features are seen in Fig. 2: a single-signed warming of the whole tropo-sphere, associated with a phase speed c ~ 50 m/s;

      6hr propagation --> 5036006 ~ 1040 km. Positive T anomaly in Fig 2b around 500hPa.

    3. The cross-isentropic flow - that is, the heating of the atmosphere by convection

      following isentropic --> conserved entropy, Cp*log(theta) cross-isentropic --> entropy/theta changes due to diabatic sources and also mixing?

    1. The cloud-resolving model (CRM) simulations wereperformed using the anelastic System for AtmosphericModeling (SAM), version 6.8.2 (Khairoutdinov andRandall 2003), for a radiative–convective equilibrium(RCE) state over an ocean surface with a sea surfacetemperature of 301.15 K

      RCE represents a balanced state of interactions between clouds and radiation.

    2. To reduce thiscomplication, we prescribed time-invariant temperatureand moisture tendencies to substantially reduce the driftin the large-scale basic state (seeappendix A). We takethe view that the prescribed tendencies affect convec-tion indirectly through their effects on the (horizontalmean) temperature and humidity profiles, and theseprofiles uniquely determine the convective statistics.

      using prescribed tendencies to maintain the shape of temperature anomaly as designed but removing induced moisture anomaly.

    3. This is achieved by tracking a total of approximately30 million Lagrangian particles/parcels (or eight per gridbox on average) embedded in the CRM

      Tracking parcels and separating them into different groups by entrainment rate/length

    4. n empirical formula was proposed to relate thefractional entrainment rate to the product of the verticalvelocity and cloud radius, and a nearly constant co-efficientawas identified within the bulk of the cloudlayer («5a/wd, wherewis the vertical velocity,dis thedistance to cloud edge, anda’0.23 m s21).

      an empirical formula for entrainment in terms of vertical velocity and cloud radius (cloud edge distance) originally for shallow cumulus. And it's also available for deep convection cases.

    5. A buoyancybarrier created by a warm anomaly will more easilyeliminate parcels with smaller vertical velocity from thecloudy updrafts, resulting in more mass flux reduction inresponse to a lower-tropospheric warm anomaly.

      parcels with smaller velocity are blocked by the buoyancy barrier caused by warm anomaly. Larger velocity will allow parcels break through the layer with a warm anomaly by reducing KE in them.

  3. Mar 2019
    1. Observed diabatic heating anomaly profiles regressed against MJO-filtered outgoing longwave radiation during TOGA-COARE as a function of time relative to the MJO peak.

      Looks like the heating modes in class, heating sources to see gravity waves propagating.

    2. shallow and midlevel-top (“congestus”) convective clouds that heat and moisten the lower troposphere are most common. As the atmosphere humidifies and destabilizes, deep convection is eventually triggered

      shallow and congestus convective clouds: destabilizing the atmosphere by heating and moistening the lower troposphere.

      deep clouds: adjust the environment by warming the upper level (latent heat, induced subsidence?) and cooling the lower one (evaporation).

    3. The lack of sensitivity can be traced in part to underestimated entrainment of environmental air into rising convective clouds and insufficient evaporation of rain into the environment. As a result, the parameterizations produce deep convection too easily while stabilizing the environment too quickly to allow the effects of convective mesoscale organization to occur.

      underestimated entrainment --> deep convection produced too easily to stabilize the environment --> no chance for organized convection to occur.

      How is entrainment presented in GCMs? a constant mixing length?

    1. Fig. 2. The 1979–99 mean DJFM precipitation (mm day−1) from (a) GPCP, (b)–(d) AMIP, and (e)–(g) CMIP sensitivity experiments.

      Double ITCZ seems to be more significant during boreal winter and in the coupled model.

      Pure atmospheric model captures the spatial structure, but precipitation tends to be overestimated in SPCZ.

    2. Fig. 1. The 1979–99 mean JJAS precipitation (mm day−1) from (a) GPCP, (b)–(d) AMIP, and (e)–(g) CMIP sensitivity experiments.

      Higher entrainment rate leads to crazy precipitation over the warm pool.

      How? more "clouds" are inhibited for the environment to accumulate higher CAPE (by moistening the lower layers through inhibited clouds?), leading to stronger rainfall?

    1. The presence of dry midtropospheric air may thus serve to help permit the buildup of buoyant energy for subsequent episodes of deep convection, such as associated with the onset of the Madden–Julian oscillation.

      drier layers aloft can build up a huge buoyancy (Tv-Tvenv is larger within dry layers) for subsequent deep convection.

      But entrainment with dry air would inhibit convection for further development, so how does that work?

    2. The entrainment of drier air results in a 37% reduction in rainfall when the dry layer extends from the 600-hPa level to the model top. Tests show that entrainment of dry air at mid levels has a major impact in suppressing precipitation production due to cold rain processes.

      cold rain processes are important for stronger precipitation.