Discover and read the best of Twitter Threads about #SJSU
Most recents (20)
6+ statements summarizing why the vast majority of climate scientists think human burning of fossil fuels is causing contemporary global warming. (1/10) #SJSU #Metr12 #GlobalWarming
1) Fundamental physics tells us that increasing greenhouse gas concentrations in the atmosphere should warm the surface, all else equal. This is so fundamental that the greenhouse effect was 1st proposed way back in 1824 (by Joseph Fourier). (2/10)
2) Through burning fossil fuels, humans have increased the concentrations of greenhouse gasses in the atmosphere. CO2 concentrations were nearly constant for thousands of years but have increased by almost 50% since the industrial revolution. (3/10)
Conservation of potential vorticity can explain typical ridge/trough airflow patterns associated with large mountain ranges #SJSU #METR171a #SynopticMeteorology
And contrary to what you may have learned in grade school, this continental-scale trough ridge pattern, induced by the Rockies, is probably more responsible for Western Europe's mild winters than anything having to do with the Gulf Stream #SJSU rmets.onlinelibrary.wiley.com/doi/abs/10.125…
Ridges above mountains result from compression of air columns, inducing negative relative vorticity and troughs on the lee side result from expansion of air columns inducing positive relative vorticity. #SJSU #METR171a #SynopticMeteorology
Potential vorticity is the vorticity an air column would have if it were brought adiabatically to some standard latitude and stretched or shrunk vertically to some standard depth #SJSU #METR171a #SynopticMeteorology
Isentropic potential vorticity is conserved under adiabatic frictionless flows #SJSU #METR171a #SynopticMeteorology
Stretching a column of air vertically can ‘spin up’ vorticity via conservation of angular momentum just like an ice skater rotating faster when they bring their arms closer to their body #SJSU #METR171a #SynopticMeteorology
Air parcels tend to flow along surfaces of constant potential temperature (isentropes). #SJSU #METR171a #SynopticMeteorology
Warm air advection is associated with air parcels ascending upsloping isentropes. This is associated with adiabatic cooling, condensation and precipitation. #SJSU #METR171a #SynopticMeteorology
Cold air advection is associated with air parcels descending downsloping isentropes. This is associated with adiabatic warming and fair weather. #SJSU #METR171a #SynopticMeteorology
There are only 3 fundamental ways to change the Earth’s energy budget: 1) Modification of incoming solar radiation, 2) Modification of the fraction of incoming solar radiation reflected back to space, 3) Modification of the Earth’s outgoing longwave radiation #SJSU #GlobalWarming
A Radiative forcing is something that causes the Earth’s radiative energy budget to become temporarily unbalanced and thus it causes a change in global average temperature. #SJSU #METR12 #GlobalWarming
A Radiative Feedback is something that changes in response to an initial radiative forcing, either amplifying the initial change or reducing the initial change. Relevant radiative feedbacks for Earth are the water vapor feedback, the ice-albedo feedback, and the cloud feedback.
All objects with a temperature above absolute zero emit electromagnetic radiation which is characterized by the peak-to-peak length of the electromagnetic waves (their wavelength) #SJSU #METR12 #GlobalWarming
The Stefan-Boltzmann Law tells us that warmer objects emit more electromagnetic radiation than colder objects and thus emit more energy #SJSU #METR12 #GlobalWarming
Wien’s Law tells us that warmer objects emit a higher proportion of their electromagnetic radiation at shorter wavelengths than cold objects #SJSU #METR12 #GlobalWarming
The quasi-geostrophic height tendency equation is a prognostic equation that tells us how synoptic-scale systems are likely to evolve in time: strengthening/weakening of highs and lows #SJSU #METR171a #SynopticMeteorology
Pressure height falls and thus the development of lows (or the weakening of highs) are associated with positive vorticity advection by the geostrophic wind and/or increasing warm air advection with height or decreasing cold air advection with height by the geostrophic wind
Pressure height rises and thus the weakening of lows (or development of highs) are associated with negative vorticity advection by the geostrophic wind and increasing cold air advection with height or decreasing warm air advection with height by the geostrophic wind
The quasi-geostrophic omega equation tells us that vertical motion in the atmosphere is related to non-geostrophic circulations that arise in order to restore thermal wind balance #SJSU #METR171a #SynopticMeteorology
Differential positive vorticity advection by the geostrophic wind and warm air advection by the geostrophic wind are associated with upward vertical motion and precipitation if sufficient moisture is present #SJSU #METR171a #SynopticMeteorology
Differential negative vorticity advection by the geostrophic wind and cold air advection by the geostrophic wind are associated with downward vertical motion and fair weather #SJSU #METR171a #SynopticMeteorology
Temperature is a measure of the average kinetic energy of the molecules in a substance which is related to the average speed of the molecules in that substance.
#SJSU #METR12 #Globalwarming
#SJSU #METR12 #Globalwarming
To increase the temperature of something (with a fixed heat capacity and no work being done) you can increase the amount of energy flowing in, while keeping the amount of energy flowing out the same.
#SJSU #METR12 #Globalwarming
#SJSU #METR12 #Globalwarming
To increase the temperature of something (with a fixed heat capacity and no work being done) you can decrease the amount of energy flowing out, while keeping the amount of energy flowing in the same. #SJSU #METR12 #Globalwarming
Humans exhale CO2 but this does not contribute to global warming because that exhaled carbon was recently obtained from the atmosphere via plant photosynthesis and thus exhaling CO2 is just cycling carbon back to where it was recently extracted. #SJSU #METR12 #Globalwarming
Over the long term (millions of years) silicate-to-carbonate conversion draws CO2 out of the atmosphere and sequesters the carbon in the seafloor. This process is too slow to have any appreciable effect on the CO2 produced from fossil fuel burning. #SJSU #METR12 #Globalwarming
The carbon sequestered on the seafloor makes it back to the atmosphere via subduction of the oceanic crust and volcanic eruptions that release CO2. #SJSU #METR12 #Globalwarming
Jet stream is maximized at mid-latitudes because that is where the meridional temperature gradient is the highest and it is maximized in the upper troposphere because that is where the temperature-gradient-caused pressure gradient is the highest #SJSU #METR171a
Jet stream is wavy because of conservation of absolute vorticity. When it meanders north, planetary vorticity increases, inducing a negative curvature vorticity to compensate. When it meanders south, planetary vorticity decreases, inducing pos curvature vorticity to compensate.
Rossby waves travel to the west relative to the background flow and longer waves travel faster to the west. Since the background flow is to the east, longer waves appear to move more slowly to the east and the longest waves can move to the west.
Each Northern Hemisphere spring, photosynthesis begins to outweigh respiration and global atmospheric concentrations of CO2 decrease. In the fall, the reverse occurs and global atmospheric concentrations of CO2 increase. #SJSU #METR12 #Globalwarming
Humans are altering the global carbon cycle by releasing a reservoir of carbon (that was previously sequestered) into the atmosphere-ocean-land system. #SJSU #METR12 #Globalwarming
The carbon that goes into the atmosphere from the burning of fossil fuels represents only a few percent of the total carbon into the atmosphere annually. But it is not compensated for and thus is responsible for all of the long-term atmospheric increase.
Dominant terms in vertical momentum equation are vertical pressure gradient force and gravitational force. #SJSU #METR171a #SynopticMeteorology
Vertical motion is of primary importance in weather forecasting because the source of heat and moisture for storms is the surface. Horizontal divergence of the wind field aloft necessarily implies vertical motion through conversation of mass. #SJSU #METR171a #SynopticMeteorology
Potential temperature tells us the temperature a parcel of air would have if it were brought down to a reference pressure level. Potential temperature is useful for diagnosing the stability of the atmosphere. #SJSU #METR171a #SynopticMeteorology
The Kaya Identity shows that one way to affect CO2 emissions would be through population-influencing policies #SJSU #METR12 #Globalwarming 
The Kaya Identity shows that one way to reduce CO2 emissions would be through reduced production/consumption of goods and services (i.e., reduced economic activity) #SJSU #METR12 #Globalwarming
The Kaya Identity shows that one way to reduce CO2 emissions would be through increasing the goods and services that can be produced for a given amount of energy (increasing energy efficiency) #SJSU #METR12 #Globalwarming
The momentum equations that we work with are just f=ma applied to the atmosphere. They say that acceleration of a parcel of air is the sum of the forces applied to that parcel (per unit mass): the pressure gradients force, the Coriolis force, and friction. #SJSU #METR171a
Scale analysis allows us to focus on which terms are most important for describing the main features of the weather phenomena we are interested in. #SJSU #METR171a #SynopticMeteorology
Scale analysis reveals that synoptic-scale weather systems are close to being in geostrophic balance where their motion is characterized by a balance between the pressure gradient force and the Coriolis force. #SJSU #METR171a #SynopticMeteorology
Fossil fuels are still used to produce around ~80% of all the energy consumed by humans
#SJSU #METR12 #GlobalWarming
#SJSU #METR12 #GlobalWarming
Fossil fuels are not equal in terms of carbon dioxide (CO2) emissions produced per unit of energy, burning coal releases more CO2 than oil which released more CO2 than natural gas. #SJSU #METR12 #GlobalWarming
Fossil fuels are a non-renewable, limited resource but there are more than enough left to radically alter the climate (~+10C) if we were to burn them all. #SJSU #METR12 #GlobalWarming
Math review (derivatives of vector and scalar fields)
1) The gradient is the directional derivative (del) applied to a scalar field. The gradient vectors represent both the local direction of greatest increase of the scalar field and the local magnitude of that increase
1) The gradient is the directional derivative (del) applied to a scalar field. The gradient vectors represent both the local direction of greatest increase of the scalar field and the local magnitude of that increase
The divergence is the directional derivative (del) applied to a vector field via the dot product. The divergence values measure the local spreading of a vector field. #SJSU #METR171a #SynopticMeteorology
The vorticity is the directional derivative (del) applied to a vector field via the X product. Vorticity values are a local measure of the propensity of adjacent vectors to produce rotation. The vorticity represents both the spatial orientation & the magnitude of that rotation.
Math review (vectors)
1) Vector fields embed information about the magnitude and direction of a quantity at each grid point in space (represented by their origin) – they are not line segments in that space.
#SJSU #METR171a #SynopticMeteorology
1) Vector fields embed information about the magnitude and direction of a quantity at each grid point in space (represented by their origin) – they are not line segments in that space.
#SJSU #METR171a #SynopticMeteorology
2) The dot product is the measure of similarity between vectors – it accumulates interactions in the same direction
3) The cross product is a measure of the difference between vectors – it accumulates interactions in different directions
I'll be tweeting the main points that we discussed in each of the meetings of the Synoptic Meteorology class I am teaching at SJSU. Here are today's, where the broad topics were the human role in forecasting and statistical postprocessing.
#SJSU #METR171a #SynopticMeteorology
#SJSU #METR171a #SynopticMeteorology
1) The value-added from human forecasters has diminished over time as dynamical models have improved/become higher in resolution and statistical postprocessing has become more sophisticated.
2) A meteorologist (or A.I. system) should be able to recognize, through experience (learning) on past data, that a given dynamical model will tend to be off in a given direction under a particular circumstance (e.g., GFS winter high temperatures during a nor'easter tend to be _)
I'll be tweeting the main points that we discussed in each of the meetings of the global warming class I am teaching at SJSU. Here are today's, where the broad topics were the current Amazon fires and fossil fuels in general.
#SJSU #METR12 #Globalwarming
#SJSU #METR12 #Globalwarming
1) Our oxygen supply is not in jeopardy due to the current Amazon fires and will not be put in jeopardy from any wildfires.
2) Almost all the energy that is available to us on Earth (including even wind energy and the energy that we use to power our bodies) originated from the nuclear reactions inside the Sun.
