Choose the correct answer options in the context of the question. In some questions you can select multiple options.
About this exercise type...Why are concentrations of NOx in the lower troposphere very variable?
| — | NO and NO2 are easily interchangeable. |
| — | Photolysis quickly splits up NO2. |
| — | There are several mechanisms for creating and destroying NOx. |
| — | HNO3 acts as a sink for NOx. |
The typical lifespan of NOx in the lower troposphere is short. What are the consequences of this fact for monitoring NOx?
| — | Concentrations of NOx in the lower troposphere can be ignored. |
| — | NOx concentrations can vary rapidly through time. |
| — | Point measurements need to be repeated at short intervals. |
| — | Concentrations of NOx tend to even out over time. |
Particular local events such as biomass burning can lead to high local values for NOx emissions. What are the consequences of this fact for monitoring NOx?
| — | NOx concentrations can vary considerably from place to place. |
| — | The distribution of NOx tends to even out over time. |
| — | Point measurements are only valid for their immediate locality. |
| — | Point measurements of NOx concentrations need to be averaged over a wider area. |
As a result of the spatial variability of the concentrations of NOx:
| — | The area of a point measurement needs to be small. |
| — | A large number of point measurements are needed to cover a wide area. |
| — | Many values for concentrations of NOx need to be interpolated from a number of point measurements. |
| — | The spatial resolution of a point measurement needs to be high. |
What are the limitations on measuring NOx concentrations on a global scale without using satellites?
| — | Ground stations cannot measure tropospheric NOx. |
| — | Aircraft measurements of NOx are inaccurate. |
| — | Many locations are inaccessible. |
| — | It is impracticable to make a long series of repeated measurements at short intervals over a large area. |
Measuring the concentrations of trace gases such as NOx in the troposphere from ground stations is difficult. Why?
| — | It is difficult to eliminate boundary layer effects. |
| — | It is difficult to obtain a reference spectrum for the solar irradiance. |
| — | It is difficult to identify weak absorbers in the measured spectra. |
| — | It is difficult to establish an altitude profile for a trace gas. |
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